Reproducibility of circumferential leg and knee joint ...

Diplomarbeit

Reproducibility of circumferential leg and knee joint

flexion measurements and clinical course of recovery

after total knee arthroplasty

eingereicht von

Dipl.-Ing. Daniela Hirzberger Geb.Dat.: 25.09.1982

zur Erlangung des akademischen Grades

Doktor(in) der gesamten Heilkunde

(Dr. med. univ.)

an der

Medizinischen Universität Graz

ausgeführt an der

Universitätsklinik für Orthopädie und orthopädische Chirurgie

unter der Anleitung von

Ass.-Prof. Priv.-Doz. Dr. Mathias Glehr

Priv.-Doz. Dr. Patrick Sadoghi

Graz, am 14. November 2013

Eidesstattliche Erklärung

Ich erkläre ehrenwörtlich, dass ich die vorliegende Arbeit selbstständig und ohne fremde

Hilfe verfasst habe, andere als die angegebenen Quellen nicht verwendet habe und die den

benutzten Quellen wörtlich oder inhaltlich entnommenen Stellen als solche kenntlich

gemacht habe.

Graz, am …… Unterschrift

Acknowledgements

Writing my diploma thesis would not have been possible without the assistance and

support of many kind people around me, only some of whom I can give particular mention

here.

First and foremost, I extend my sincerest gratitude to all participants and observers who

have willingly shared their precious time. Kathi, Mathias, Michi, Rosaleen, Sandra, Anna,

Angela, Claudia, Gerhard, Gottfried, Irene, Ivo, Johannes, Joseph, Margit, Marie-Therese,

Markus, Oli, Patricia, Peter, Regina, Simone, Thomas, Wolfgang - this study would not

have been possible without you.

I owe my deepest gratitude to my supervisor Ass.-Prof. Priv.-Doz. Dr. Mathias Glehr, who

suggested this topic to me and supported me throughout the study with his continuous

optimism and knowledge, whilst allowing me the room to work in my own way. I also

express my warmest gratitude to my other supervisor Priv.-Doz. Dr. Patrick Sadoghi

whose useful comments, remarks and engagement helped me through the learning process.

I am deeply grateful to Univ. Prof. Dr. Andreas Leithner, Head of the Department of

Orthopaedics and Orthopaedic Surgery, for giving me the opportunity to conduct my study

at his department and introducing me to scientific working and writing.

I wish to thank Univ.-Ass. Mag. Dr. Alexander Avian and Dr. Gerwin Bernhardt, who

patiently answered all my questions concerning statistics. I also thank Dr. Lukas Holzer

for his interest in my thesis and for his encouraging words time and again.

I sincerely thank all of the medical and nursing staff of the Department of Orthopaedics

and Orthopaedic Surgery, whose daily routine I disturbed with my measurements time and

again.

Finally, I am deeply grateful to my parents and my sister Sandra for their love and

continuous support – both spiritually and materially.

Abstract

Background: Knee swelling after total knee arthroplasty (TKA) may lead to pain and loss

of motion. In clinical practice, postsurgical swelling is recorded by means of

circumferential measurements using tape measures, while the knee range of motion (ROM)

may be assessed by goniometric measurements. The first objective of this study was to

determine inter-observer and intra-observer reproducibility (in terms of reliability and

agreement) of circumferential leg and knee flexion measurements. The second aim was to

evaluate recovery of in-patients following TKA with respect to postoperative swelling,

passive knee ROM and pain intensity, and to determine a possible influence of postsurgical

swelling on passive ROM.

Methods: For reproducibility of circumferential and goniometric measurement, two

observers examined 40 legs of 20 healthy adults. Circumferential measurements were

obtained at three measurement sites (mid-patella, 7 cm proximal of mid-patella, 7 cm distal

of mid-patella), using four different types of tape measures (standard tape measure,

circumference tape measure, Gulick I tape measure, Gulick II plus tape measure). Knee

flexion was measured with a short-arm universal goniometer in two standardised knee joint

positions. Agreement was quantified by calculation of the smallest detectable difference

(SDD), and reliability by means of the intraclass correlation coefficient (ICC2,1).

Clinical assessment was undertaken in 29 patients undergoing TKA. This included lower

limb girths at the three measurement sites mentioned above, passive knee ROM, and knee

pain intensity using a Numerical Rating Scale (NRS). Pearson´s correlation coefficient was

computed to establish a possible relationship between circumference change and passive

ROM.

Results: In the circumference study, inter-tester agreement (SDD) ranged from 0.7 to 2.1

cm and intra-tester agreement from 0.9 to 1.7 cm. The circumference measurements were

generally reliable (ICC2,1 > 0.93). Considering the different measurement sites, agreement

was lowest at 7 cm proximal of mid-patella. Comparing the different tape measures used,

the Gulick II plus tape measure showed the lowest level of agreement (SDD range, 0.8-2.1

cm). Agreement was highest for the circumference tape measure (SDD range, 0.7-1.2 cm).

In knee joint flexion measurements, the level of agreement (SDD) ranged from 5.9 to 9.0°

for inter-observer and 7.1 to 8.1° for intra-observer comparisons. Reliability (ICC2,1)

ranged from 0.85 to 0.99.

Lower limb swelling occurred in all patients after TKA surgery. The circumference change

was higher above the knee (mean 5.1 cm, range, 2.3-7.6 cm) than at mid-patella (mean 3.8

cm, range, 1.9-9.8 cm) and below the knee (mean 2.8 cm, range, 1.7-7.2 cm). Maximum

swelling was reached on the third to fourth postoperative day. Passive ROM increased

continuously after TKA. On sixth postoperative day, the mean passive ROM was 79.0°

(range, 55-100°). Circumference change at the three measurement positions did not show

any significant correlation with passive ROM on third and sixth postoperative day

(P≥0.1375). Postsurgical pain intensity reported by the patients was highest preoperatively

(mean NRSmax 7.0, range 4-9), which might be explained by the patient-controlled

analgesia for 72 hours postoperatively. After surgery, pain intensity decreased

continuously until dismissal day (mean NRSmax 3.0, range 1-9).

Conclusion: In circumferential measurements, the level of reproducibility differed

substantially depending on the measuring position and tape measure used. With the

circumference tape measure, differences in girth exceeding 1.2 cm can be considered a real

change above measurement error. Measuring knee flexion with a short-arm universal

goniometer, differences of less than 9° cannot be distinguished from measurement error.

After TKA, swelling in the knee region was observed in all patients, but did not seem to

influence passive ROM after TKA surgery.

Zusammenfassung

Einleitung: Nach der Implantation einer Knietotalendoprothese (KTEP) kann eine

Schwellung im Bereich des Kniegelenks auftreten, die zu Schmerzen und einem

verminderten Bewegungsumfang (range of motion/ROM) führen kann. Die postoperative

Schwellung kann durch Umfangsmessungen mit einem Maßband erfasst und der

Bewegungsumfang durch Messungen mit einem Goniometer beurteilt werden. Ein Ziel

dieser Arbeit war, die Reproduzierbarkeit (im Sinne von Übereinstimmung und

Reliabilität) von Umfangsmessungen und Messungen der Knieflexion zu bestimmen.

Weiters sollte der klinische Verlauf nach KTEP-Operation in Bezug auf die postoperative

Schwellung, den passiven ROM und die Schmerzintensität beurteilt werden.

Methoden: Zur Beurteilung der Reproduzierbarkeit von Umfangs- und

Flexionsmessungen haben zwei Prüfer die Beine von 20 gesunden Probanden untersucht.

Die Umfangsmessungen erfolgten mit vier verschiedenen Maßbändern (Standard-,

Umfangs-, Gulick I-, Gulick II plus-Maßband) an drei Messpositionen im Bereich des

Kniegelenks (Patella-Mitte, 7 cm proximal der Patella-Mitte und 7 cm distal der Patella-

Mitte). Die Knieflexionsmessungen wurden mit einem Universal-Goniometer in zwei

standardisierten Kniepositionen durchgeführt. Die Übereinstimmung wurde mittels

kleinster erfassbarer Messwertdifferenz (smallest detectable difference/SDD) und die

Reliabilität mittels Intraklassen-Korrelations-Koeffizienten (ICC) erfasst.

Zur Evaluierung des postoperativen Verlaufs wurden Umfangsmessungen an den oben

genannten Messpositionen durchgeführt und der passive Bewegungsumfang mit einem

Universal-Goniometer erfasst. Die Schmerzen im Bereich des Kniegelenks wurden mittels

numerischer Bewertungsskala (Numerical Rating Scale/NRS) erhoben. Um eine mögliche

Korrelation zwischen Umfangsänderung und passivem ROM festzustellen, wurde der

Pearson´s Korrelationskoeffizient berechnet.

Ergebnisse: Die Interrater-Übereinstimmung (SDD) der Umfangsmessungen umfasste

einen Bereich von 0.7-2.1 cm und die Interrater-Übereinstimmung einen Bereich von 0.9-

1.7 cm. Die Umfangsmessungen waren generell zuverlässig (ICC>0.93). Die

Reproduzierbarkeit zeigte eine Abhängigkeit von der Messposition und war 7 cm proximal

der Patella-Mitte am niedrigsten. Von den getesteten Maßbändern zeigte das Gulick II

plus-Maßband die geringste Übereinstimmung (SDD 0.8-2.1 cm). Die Übereinstimmung

war für das Waegener Maßband am höchsten (SDD 0.7-1.2 cm).

Die Interrater-Übereinstimmung der Knieflexionsmessungen umfasste einen Bereich von

5.9- 9.0° und die Intrarater-Übereinstimmung einen Bereich von 7.1-8.1°. Die Reliabilität

(ICC) reichte von 0.85-0.98.

Postoperative wurde bei allen KTEP-Patienten eine Schwellung im Kniebereich

beobachtet, wobei die Umfangszunahme 7 cm proximal der Patella-Mitte am höchsten war

und die maximale Schwellung zwischen dem dritten und vierten postoperativen Tag

erreicht wurde. Der passive ROM nahm im Rahmen des stationären Aufenthaltes

kontinuierlich zu und erreichte einen mittleren Wert von 79.0° (55-100°) am sechsten

postoperativen Tag. Die Umfangsänderungen zeigten keine signifikante Korrelation mit

dem passive ROM (P≥0.1375). Die anhand der NRS ermittelten Schmerzen waren

präoperativ höher als postoperativ und nahmen postoperativ bis zum Tag der Entlassung

kontinuierliche ab.

Diskussion: Die Reproduzierbarkeit von Umfangsmessungen mit Maßbändern ist von der

Messposition und dem verwendeten Maßband abhängig. Unterschiede im Beinumfang

über 1.2 cm können als tatsächliche Veränderung über dem Messfehlerbereich beurteilt

werden, wenn die Messung mit dem Umfangs-Maßband durchgeführt wird. Wenn die

Knieflexion mit einem Universalgoniometer gemessen wird, sind gemessene Unterschiede

unter 9° nicht vom Messfehler zu unterscheiden. Postoperativ wurde bei allen Patienten

eine Schwellung im Kniebereich beobachtet, die jedoch keinen Einfluss auf den passiven

Bewegungsumfang nach TKA hatte.

Table of contents V

Table of contents

Abstract ................................................................................................................................... I

Zusammenfassung ............................................................................................................... III

Table of contents .................................................................................................................. V

List of abbreviations and glossary .................................................................................... VIII

List of figures ....................................................................................................................... X

List of tables ....................................................................................................................... XII

1 Introduction ................................................................................................................... 1

1.1 Aim ......................................................................................................................... 1

1.2 Total knee arthroplasty ........................................................................................... 2

1.2.1 Indications and contraindications for TKA ..................................................... 3

1.2.2 Technique ........................................................................................................ 4

1.2.3 Risks and complications .................................................................................. 6

1.2.4 Postoperative swelling ................................................................................... 10

1.3 Methods to evaluate knee swelling ....................................................................... 10

1.4 Methods to evaluate knee flexion ......................................................................... 11

1.5 Methods to evaluate pain ...................................................................................... 13

1.6 Measurement error, Agreement and Reliability ................................................... 14

1.6.1 Measurement error ......................................................................................... 14

1.6.2 Terms reproducibility, agreement, reliability and responsiveness ................ 15

1.6.3 Statistical Methods to assess reproducibility ................................................. 16

1.7 Study hypothesis ................................................................................................... 21

2 Methods and Materials ................................................................................................ 22

2.1 Reliability and agreement measurements ............................................................. 22

2.1.1 Subjects and observers .................................................................................. 22

2.1.2 Measuring devices ......................................................................................... 24

2.1.3 Measurement procedures ............................................................................... 28

2.1.3.1 Girth measurements ................................................................................... 28

2.1.3.2 Goniometric measurements ....................................................................... 30

2.2 Clinical course after TKA ..................................................................................... 31

2.2.1 Patients .......................................................................................................... 31

2.2.2 Data acquisition ............................................................................................. 33

2.3 Statistical methods ................................................................................................ 34

Table of contents VI

3 Results ......................................................................................................................... 36

3.1 Reliability and agreement of girth measurements ................................................ 36

3.1.1 Descriptive statistics ...................................................................................... 36

3.1.2 Inter-observer reproducibility ........................................................................ 37

3.1.3 Intra-observer reproducibility ........................................................................ 41

3.2 Reliability and agreement of knee flexion measurements .................................... 44

3.2.1 Descriptive statistics ...................................................................................... 44

3.2.2 Inter-observer reproducibility ........................................................................ 44

3.2.3 Intra-observer reproducibility ........................................................................ 45

3.3 Clinical Course after TKA .................................................................................... 47

3.3.1 Changes in lower limb girth .......................................................................... 47

3.3.2 Changes in passive range of motion .............................................................. 49

3.3.3 Changes in pain intensity (NRS) ................................................................... 49

3.3.4 Relationship between girth, ROM and pain changes .................................... 50

3.3.5 Postoperative follow up examination six weeks after TKA .......................... 52

3.3.6 Influence of gender and BMI on postoperative swelling .............................. 53

3.3.7 Subjective judgment of knee swelling vs. girth measurements ..................... 54

4 Discussion .................................................................................................................... 55

4.1 Discussion of the girth reproducibility measurements ......................................... 55

4.1.1 Discussion of the results ................................................................................ 55

4.1.2 Sources of measurement error ....................................................................... 63

4.1.3 Usability of the different tape measures ........................................................ 68

4.2 Discussion of the flexion reproducibility measurements ...................................... 71

4.2.1 Discussion of the results ................................................................................ 71

4.2.2 Sources of measurement error ....................................................................... 76

4.3 Discussion of the statistical methods .................................................................... 79

4.4 Clinical course ...................................................................................................... 80

5 Conclusion ................................................................................................................... 81

6 References ................................................................................................................... 83

A Appendix ..................................................................................................................... 93

A.1 Results of the second measuring day .................................................................... 93

A.1.1 Inter-observer reproducibility of girth measurements (t2) ............................ 93

A.1.2 Inter-observer reproducibility of goniometric measurements (t2) ................ 96

A.2 Results of the observers O1, O2, O3, O4 and O5 ................................................. 97

VII

A.2.1 Reproducibility of girth measurements (O1-O5)........................................... 97

A.2.2 Reproducibility of goniometric measurements (O1-O5) ............................. 109

A.3 Additional tables and figures of observers O1 and O2 ....................................... 112

A.3.1 Reproducibility of girth measurements (first measuring day) ..................... 112

A.3.2 Reproducibility of knee flexion measurements ........................................... 116

A.4 Additional figures of clinical course measurements ........................................... 117

Questionnaire on the usability of the measuring tapes .................................................. 119

Probandeninformation/Einwilligungserklärung ............................................................ 123

List of abbreviations and glossary VIII

List of abbreviations and glossary

ANOVA Analysis of variance

B-A Bland and Altman

BMI Body mass index, unit: kg/m2

CI Confidence interval

CD Critical difference

cm Centimetre, 1 cm = 10-2

m

CR Coefficients of repeatability

CV Coefficient of variation

D Difference

DP Measurement site 7 cm distal of mid-patella

e.g. Exempli gratia

et al. Et alii/ et aliae/ et alia

g Gram, = unit of weight (SI)

GI Gulick I tape measure

GII Gulick II plus tape measure

ICC Intraclass correlation coefficient

in Inch, 1 in = 2.54 cm

kg Kilogram, 1 kg = 103 g

KROM Knee range of motion

i.e. Id est

l Left leg

L Length (of goniometer arms)

LOA Limits of agreement

m Meter, = unit of length (SI)

m2 Square meter, = unit of area (SI)

mD Mean difference

MP Measurement site at mid-patella

n Sample size

NRS Numeric rating scale

O Observer

oz Ounce, non-metric unit of mass, 1 oz = 28,349523125 g

r Right leg

ROM Range of motion

List of abbreviations and glossary IX

PP Measurement site 7 cm proximal of mid-patella

RP Relative precision

S Standard tape measure

SD Standard Deviation

SDD Smallest detectable difference

SEM Standard error of measurement

TKA Total knee arthroplasty

VAS Visual analogue scale

VRS Verbal rating scale

vs. Versus

W Waegener tape measure

° Degree, = unit of measurement for angles

List of figures X

List of figures

Figure 1: The 10 most frequent medical services in Austria in the year 2011 ...................... 2

Figure 2: Number of TKA surgeries performed in Austria from 2004 to 2011 .................... 3

Figure 3: Scheme of total knee arthroplasty .......................................................................... 5

Figure 4: Scales to evaluate pain (VAS, NRS, VRS) .......................................................... 14

Figure 5: Example for a Bland and Altman plot ................................................................. 20

Figure 6: Number of subjects (girth measurements) ........................................................... 23

Figure 7: Number of subjects (knee flexion measurements) ............................................... 24

Figure 8: Standard tape measure ......................................................................................... 25

Figure 9: Waegener circumferential tape measure .............................................................. 25

Figure 10: Gulick I tape measure ........................................................................................ 26

Figure 11: Tension indicators of the Gulick I (left) and Gulick II tape measures (right) ... 27

Figure 12: The Gulick II plus tape measure ........................................................................ 27

Figure 13: Universal Goniometer ........................................................................................ 28

Figure 14: Subject positioning for girth measurements....................................................... 29

Figure 15: Anatomic landmarks used for the alignment of the universal goniometer ........ 30

Figure 16: First positioning device and subject in position P2............................................ 30

Figure 17: Second positioning device and subject in position P2 ....................................... 31

Figure 18: Girth - Inter-observer B-A plots at PP for the observers O1 and O2 ................. 39

Figure 19: Girth - Inter-observer B-A plots at MP for the observers O1 and O2 ............... 40

Figure 20: Girth - Inter-observer B-A plots DP for the observers O1 and O2 .................... 40

Figure 21: Girth - Intra-observer B-A plots at PP for the observers O2 ............................. 42

Figure 22: Girth - Intra-observer B-A plots at PP for the observers O2 ............................. 43

Figure 23: Flexion - Inter-observer B-A plots for the observers O1 and O2 ...................... 45

Figure 24: Flexion - Intra-observer B-A plots for the observers O1 and O2 ...................... 46

Figure 25: Changes in mean girth of the operated lower leg............................................... 47

Figure 26: Changes in mean girth of the operated and the contralateral leg ....................... 48

Figure 27: Changes in mean passive ROM ......................................................................... 49

Figure 28: Changes in mean minimum and maximum NRS ............................................... 50

Figure 29: Clinical course - Girth at PP and passive ROM ................................................. 50

Figure 30: Clinical course - Girth at PP and maximum reported NRS ............................... 51

Figure 31: Clinical course – Passive ROM and maximum NRS ......................................... 51

Figure 32: Subjective judgment of swelling in the knee region by patients........................ 54

List of figures XI

Figure 33: Scales of the used tape measure ......................................................................... 66

Figure 34: Influence of different positioning devices ......................................................... 77

Figure 35: B-A plots vs. scatter plots ................................................................................. 79

Figure 36: Girth - Inter-observer B-A plots at PP for the observers O1 and O2 (t2) .......... 94

Figure 37: Girth - Inter-observer B-A plots at MP for the observers O1 and O2 (t2) ......... 95

Figure 38: Girth - Inter-observer B-A plots at DP for the observers O1 and O2 (t2) ......... 95

Figure 39: Flexion - Inter-observer B-A plots for second measuring day (O1 and O2) ..... 96

Figure 40: Girth - Intra-observer B-A plots at PP for the observer O1 (n=10 legs) .......... 102





Figure 45: Girth - Intra-observer B-A plots at MP for observer O1 (n=10 legs) .............. 104





Figure 50: Girth - Intra-observer B-A plots at DP for observer O1 (n=10 legs) ............... 107





Figure 55: Flexion - Intra-observer B-A plots for the observers O1-O5 ........................... 111

Figure 56: Girth - Intra-observer B-A plots at MP for the observers O1 and O2 ............. 114

Figure 57: Girth - Intra-observer B-A plots at DP for the observers O1 and O2 .............. 115

Figure 58: Relationship between mean girth at MP and mean passive ROM ................... 117

Figure 59: Relationship between mean girth at DP and mean passive ROM.................... 117

Figure 60: Relationship between mean Girth at MP and maximum reported NRS .......... 118

Figure 61: Relationship between mean Girth at DP and maximum reported NRS ........... 118

List of tables XII

List of tables

Table 1: Statistical methods used in circumferential and goniometric reliability studies ... 17

Table 2: ICC types and corresponding SPSS/MedCalc model............................................ 19

Table 3: Observers ............................................................................................................... 22

Table 4: Characteristics of patient sample (n=29) ............................................................... 32

Table 5: Inclusion and exclusion criteria (patients)............................................................. 32

Table 6: Data acquisition ..................................................................................................... 34

Table 7: Descriptive statistics for the circumference measurements .................................. 36

Table 8: Girth - Inter-observer reproducibility for observers O1 and O2 (n=40 legs) ........ 38

Table 9: Girth - Intra-observer reproducibility for observers O1 and O2 ........................... 41

Table 10: Descriptive statistics for the goniometric measurements .................................... 44

Table 11: Flexion – Inter-observer reproducibility for observers O1 and O2 (n=38 legs) . 44

Table 12: Flexion – Intra-observer reproducibility for observers O1 and O2 (n=34 legs) . 46

Table 13: 6-weeks check: Changes in girth and PROM ...................................................... 52

Table 14: Effects of BMI and gender on lower extremity swelling after TKA ................... 53

Table 15: Girth - Summary of the results (observers O1 and O2) ...................................... 55

Table 16: Girth - Inter-observer reproducibility for observers O1 and O2 (n=40 legs) ...... 57

Table 17: Comparison of measuring tapes .......................................................................... 59

Table 18: Girth - Intra-observer reproducibility for the observers O1-O5 (n= 10 legs) ..... 61

Table 19: Percentage of differences exceeding 1 cm, 1.5 cm, and 2 cm (O1-O5) .............. 62

Table 20: Mean difference in measured patella length for the observers O1-O5 ................ 64

Table 21: Girth - Inter-observer reproducibility of first and second measuring day ........... 67

Table 22: Left and right leg intra-observer comparisons (SDD and ICC) (n=18) .............. 68

Table 23: Flexion: Summary of the results (observers O1 and O2) .................................... 71

Table 24: Knee flexion in literature ..................................................................................... 73

Table 25: Flexion - Intra-observer repeatability (observers O1-O5) ................................... 76

Table 26: Flexion - Inter-observer reproducibility of first and second measuring day ....... 77

Table 27: Agreement for the positioning devices PD1 and PD2 ......................................... 78

Table 28: Flexion – Left and right leg side differences ....................................................... 78

Table 29: Girth - Inter-observer agreement on second measuring day (O1 and O2) .......... 93

Table 30: Girth - Inter-observer reliability (ICC) on second measuring day (O1 and O2) . 94

Table 31: Flexion - Inter-observer reproducibility on second measuring day (O1 and O2) 96

Table 32: Girth - Inter-observer reliability for the observers O1-O5 (n=10 legs) ............... 97

List of tables XIII

Table 33: Girth - Inter-observer reliability (ICC) on second measuring day (O1-O5) ....... 98

Table 34: Girth - Intra-observer agreement of observer O1 (n=10 legs)............................. 98



Table 37: Girth - Intra-observer agreement of observer O4 (n=10 legs)........................... 100

Table 38: Girth - Intra-observer agreement of observer O5 (n=10 legs)........................... 100

Table 39: Girth - Intra-observer reliability for the observers O1-O5 ................................ 101

Table 40: Flexion - Inter-observer reliability (ICC) for observers O1-O5 (n=5) .............. 109

Table 41: Flexion - Intra-observer agreement for observers O1–O5 ................................ 110

Table 42: Flexion - Intra-observer reliability (ICC) for observers O1-O5 (n=5) .............. 110

Table 43: Girth - Inter-observer agreement for first measuring day (O1 and O2) ............ 112

Table 44: Girth - Intra-observer agreement for observer O1............................................. 113

Table 45: Girth - Intra-observer agreement for observer O2............................................. 113

Table 46: Flexion - Inter-observer reproducibility for O1 and O2 (t1, n=38 legs) ........... 116

Table 47: Flexion - Intra-observer reproducibility for observer O1 (n=34 legs) .............. 116

Table 48: Flexion - Intra-observer reproducibility for observer O2 (n=34 legs) .............. 116

Introduction - Aim 1

1 Introduction

1.1 Aim

Total knee arthroplasty (TKA) is currently the international standard of care for treating

severe degenerative and rheumatic knee joint disease, as well as certain knee joint fractures

[1]. Swelling of the involved lower limb after TKA due to intraarticular bleeding and

inflammation of the periarticular tissues is common and can cause pain, extended bed-rest,

and a delay in rehabilitation [2,3]. Thus, reduction in swelling and restoration of knee joint

range of motion (ROM) are important components in the overall postoperative

rehabilitation [4]. In order to monitor and guide rehabilitation, tape measures and universal

goniometers are frequently used instruments in the assessment of swelling and ROM of the

knee, respectively [4]. However, a basic prerequisite for any measurement to be of value is

a sufficient degree of repeatability in order to allow an observer to recognize some change

from normal [5]. Thus, the first aim of this study was to determine the reproducibility of

circumference measurements in the knee region using four different types of tape

measures. Besides that, the reproducibility of goniometric measurements using a standard

goniometer with special attention to clinical application should be evaluated. In particular,

the analysis aimed at answering the following questions

- How reproducible are girth/goniometric measurements?

- Does the measurement site/test position have an influence on reproducibility?

- Which tape measure is most accurate?

- Does tester experience matter?

The second aim of this study was to evaluate the course of in-patient recovery after total

knee arthroplasty and to establish a possible relationship between postsurgical swelling and

passive ROM. For this purpose, the course of rehabilitation for patients undergoing TKA at

the Department of Orthopaedic Surgery, Medical University of Graz, was recorded by

means of circumferential measurements in the knee region, measurements of passive

ROM, and a pain intensity score (NRS).

Introduction - Total knee arthroplasty 2

1.2 Total knee arthroplasty

In the year 2011, the most frequent surgical procedures in Austria were cataract surgery,

followed by dermatological operations, vaginal delivery and knee joint surgeries [6].

Among the ten most frequently performed surgical procedures, total knee arthroplasty

(TKA) ranked in eighth place (Figure 1). Thus, TKA is a very commonly performed, major

orthopaedic procedure.

Figure 1: The 10 most frequent medical services in Austria in the year 2011

Source: STATISTIK AUSTRIA [6]

Over the past 10 years, there has been a considerable increase in the amount of primary

arthroplastic knee joint replacement (Figure 2). Between 1999 and 2011, the incidence of

total knee replacement surgery in Austria has more than doubled. At present,

approximately 17 400 total knee joint arthroplasties are performed each year in Austria [6].

This might be due to the fact, that, knee replacement surgery is most commonly performed

in people with advanced osteoarthritis. Osteoarthritis of the knee is one of the most

common causes of disability. As the older adult and obese populations grow, osteoarthritis

of the knee continues to increase in prevalence [7].

0 20 000 40 000 60 000 80 000 100 000

Cholecystectomy - laparascopic

Total hip arthroplasty

Total knee arthroplasty

Radical varicose vein surgery (stripping)

Cesarean section

Curettage

Arthroscopic surgery of the knee joint

Vaginal delivery

Other surgery - skin, skin appendages, subcutis

Cataract eye surgery with lens implants

Most frequent documented medical interventions in Austria 2011


Figure 2: Number of TKA surgeries performed in Austria from 2004 to 2011

Source: STATISTIK AUSTRIA [6,8-18]

1.2.1 Indications and contraindications for TKA

The primary indication for primary TKA is pain caused by severe osteoarthritis with

impairment of daily function, detoriating health-related quality of life and radiological

signs of osteoarthritis [19,20]. Further, in patients with moderate arthritis and variable

levels of pain, deformity can become the principal indication for arthroplasty when the

progression of deformity begins to threaten the expected outcome of an anticipated

arthroplasty. An occasional indication for arthroplasty in the absence of complete cartilage

space loss is severe pain from chondrocalcinosis and pseudogout in an elderly patient.

Rarely, arthroplasty may be justified in severe patellofemoral arthritis [20].

“The primary goals of joint arthroplasty in the treatment of arthritic disease are pain relief

and restoration of function and health-related quality of life” [19].

Before surgery is considered, conservative treatment measures should be exhausted.

Conservative, nonsurgical interventions for pain associated with osteoarthritis of the knee

include non-steroidal anti-inflammatory drugs (NSAIDs), certain non-narcotic analgesics,

and intra-articular injections with corticosteroids or viscosupplements [21]. Furthermore,

surgical arthroscopy may be considered. Other important modalities in early management

include physical training and weight loss [19,22].

TKA surgery should be considered in patients with persistent, moderate-to-severe pain

associated with activity despite nonsurgical interventions that are medically

fit and are

willing to accept the risks associated with the operation. There should be radiographic

evidence of significant joint damage. If there appears to be inconsistency between the

7 000

9 000

11 000

13 000

15 000

17 000

19 000

1999 2001 2003 2005 2007 2009 2011

Nu

mb

er o

f T

KA

su

rger

ies

Year


radiographic image and symptoms, other explanations for the patient’s pain

should be

considered [21].

The patient’s ability and willingness to participate in an aggressive regimen of

postoperative physical therapy is an essential factor to take into account in considering

surgery. For a good postsurgical result, vigorous physical rehabilitation, including

exercises specifically intended to require early and repetitive motion of the affected knee

despite substantial pain, is necessary. The outcome can permanently be prejudiced due to

failures of rehabilitation, which often stem from problems in managing

postoperative pain

early on [21].

Contraindications to TKA include recent or current infection, a remote source of ongoing

infection, extensor mechanism discontinuity or severe dysfunction, recurvatum deformity

secondary to muscular weakness, untreated thrombophilias and bleeding disorders, severe

vascular disease or neurologic disease affecting sensory or motor function

in the affected

leg, and inadequate soft tissue to cover the joint

[20,21].

1.2.2 Technique

The TKA operation consists of removal of the damaged cartilage, correction of joint

deformities, and replacement of the worn cartilaginous bearing surfaces on the femur, tibia,

and, optionally, patella, with an artificial bearing [21].

The most widely accepted approach uses an anterior, medial parapatellar capsular,

longitudinal incision. It is started at the medial one-third of the patellar tendon three

centimetres above the superior pole of patella, curves round the medial aspect of patella

with at least 1 cm of the medial retinaculum attached to the patella and ends 1 cm medial to

the tibial tubercle [23]. The Hoffa´s fat pad is partly resected to improve sight and reduce

volume [24]. Then, retractors are placed in a fixed position for maximal exposure and the

tibiofemoral joint is dislocated. The patella is everted laterally, allowing exposure of the

distal end of the femur, and the proximal end of the tibia and the knee hyperflexed. The

cartilages and the anterior cruciate ligament are removed. The posterior cruciate ligament

may also be removed but the tibial and fibular collateral ligaments are preserved. The ends

of femur and tibia are then accurately cut to shape using cutting guides oriented to the long

axis of the bones. Cutting jigs and anatomic landmarks are used to determine the depth and

orientation of tibial and femoral bone resections. Precise resections are made in the distal

end of the femur, the proximal end of the tibia, and, optionally, the posterior surface of the

patella to fit the corresponding surfaces of the three arthroplasty components (Figure 3). A


round ended implant is used for the femur, mimicking the natural shape of the joint. The

femoral component is typically made of metal (most commonly, a cobalt–chromium alloy).

On the tibia the component is flat, although it sometimes has a stem which goes down

inside the bone for further stability. The tibial implant is usually made of metal (either a

titanium or a cobalt–chromium alloy). A flattened or slightly dished high density

polyethylene surface is then inserted onto the tibial component so that the weight is

transferred metal to plastic, not metal to metal. There is an exchangeable polyethylene

bearing on the tibia, which makes it possible to replace the plastic articular surface without

replacing the metal component if wear of the bearing surface occurs. During the operation

any deformities must be corrected, and the ligaments balanced so that the knee has a good

range of movement and is stable and aligned. Careful attention to ligament balancing and

protecting neurovascular structures must be maintained. Trial implants

then are placed over

the resected bone surfaces; joint stability, ligament balance, and range of motion then are

assessed [21]. If satisfactory, final components are inserted (Figure 3), hemostasis is

obtained and the joint is irrigated and closed [21].

Figure 3: Scheme of total knee arthroplasty

Source: Leopold SS. N Engl J Med 2009 [21]


In some cases the articular surface of the patella is also removed and replaced by a

polyethylene button cemented to the posterior surface of the patella.

In TKA surgery, surgical management and successful clinical outcomes rely on accurate

soft tissue balancing, well positioned components and a neutrally aligned axis [22].

1.2.3 Risks and complications

As with other major surgery, complications may occur during and after TKA operation.

These include general postoperative complications, infection, venous thromboembolism,

stiffness, patellofemoral complications, peripheral nerve injury, vascular complications,

ligament injury, periprosthetic fracture, knee joint dislocation and prosthesis failure.

Obesity, increasing age, and medical comorbidities increase the risk of postoperative

complications in patients undergoing TKA [25].

1.2.3.1 Infection

The most serious complication is infection of the joint, which occurs in 1-2% of patients

within one year after surgery [21,25,26]. While it is a relatively infrequent, periprosthetic

infection remains one of the most challenging complications of joint arthroplasty [27].

The underlying diagnosis leading to TKA seems to have an influence on the incidence of

postoperative infections. Arthritic diseases other than osteoarthritis, such as posttraumatic

osteoarthritis, seropositive rheumatoid arthritis, as well as fractures around the knee,

showed increased rates of infections [28].

Such infections are likely to arise from bacterial contamination at the time of surgery [25].

Infection should be considered in patients with a consistently painful TKA and especially

in patients with a previously pain-free arthroplasty. A history of swelling, erythema, or

prolonged wound drainage is suggestive of infection, although these signs are not

uniformly present.

Basic treatment options include antibiotic suppression, debridement with prosthesis

retention, resection arthroplasty, knee arthrodesis, one-stage or two-stage reimplantation,

and knee-above amputation as last option in the case of life-threatening infection or

persistent local infection with massive bone loss [20,26]. Considering antibiotic

suppression, the choice of prophylactic antibiotics is a first generation cephalosporin, such

as cefazolin, because the most common organisms causing postoperative infection are

Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus species [20].


1.2.3.2 Venous thromboembolism

Venous thromboembolism is a potentially fatal complication after TKA [25,29]. There is a

substantial risk of developing deep vein thrombosis (DVT) and pulmonary embolism (PE)

after TKA surgery [30]. Deep vein thrombosis is common even with appropriate

thromboprophylaxis and occurs in up to 15% of patients, being symptomatic in 2 to 3%

[21]. The overall incidence of DVT after TKA without prophylaxis has been reported to

range from 40% to 88%. The risk of asymptomatic PE may be as high as 10% to 20%, with

symptomatic PE reported in 0.5% to 3% of patients and a mortality rate up to 2% [20].

During and after TKA, factors significant in the development of venous thrombosis like

venous stasis, injury to the vascular endothelium, and release of tissue thromboplastin

commonly occur [30]. Further, age over 40 years, female gender, obesity, varicose veins,

smoking, hypertension, diabetes mellitus, and coronary disease are factors that have been

correlated with an increased risk of DVT [20].

Considering the location of the DVT, proximal thrombi, in the popliteal vein and above,

are more common than thrombi in calf veins and have a higher potential to cause PE than

thrombi in calf veins [20,30].

As late sequelae, 50% to 60% of patients with symptomatic proximal vein thrombosis and

30% of those with symptomatic calf vein thrombosis develop chronic venous insuffiency

[30].

Methods of DVT prophylaxis include mechanical compression stockings or foot pumps

and pharmaceutical agents including low-dose warfarin and low-molecular-weight heparin.

Pharmacological prophylaxis of DVT in TKA decreases the frequency of fatal pulmonary

embolism and is thus strongly indicated [20].

1.2.3.3 Patellofemoral complications

Patellofemoral complications include patellofemoral instability, patellar fracture,

component failure, patellar component loosening, patellar clunk syndrome, and extensor

mechanism tendon rupture and have been cited as the most common reasons for

reoperation [20].

“Patellofemoral instability can be caused by a number of factors, including extensor

mechanism imbalance with a tight lateral retinaculum associated with preoperative valgus

deformity, excessive lateral patellar facet resection, lateral placement of the patellar

component with failure to reproduce the normal position of the median eminence, and

early postoperative rupture of the medial capsular repair” [20].


Patellar fracture after TKA is uncommon and has been correlated with multiple factors,

including excessive patellar resection, vascular compromise secondary to lateral release,

patellar maltracking secondary to component malposition, excessive joint line elevation,

knee flexion of more than 115 degrees, trauma, thermal necrosis from PMMA

polymerization, and revision TKA [20].

“Patellar component loosening occurs in approximately 0.6% to 2% of arthroplasties”

[20]. Deficient bone stock, component malposition and subluxation, patellar fracture,

avascular necrosis of the patella, and loosening of other knee components are predisposing

factors.

In patellar clunk syndrome, a fibrous nodule forms on the posterior surface of the

quadriceps tendon just above the superior pole of the patella. This nodule can become

entrapped in the intercondylar notch of the femoral prosthesis and cause the knee to pop or

“clunk” at approximately 30 to 45° of knee flexion as the knee is actively extended. The

recommended treatment for patellar clunk syndrome is open or arthroscopic debridement

of the nodule, with possible revision of the patellar component [20].

“Rupture of the quadriceps or patellar tendon is an infrequent but severe complication of

TKA” [20]. In part, quadriceps rupture may be related to lateral release because of vascular

comprise of the tendon and possibly with extension of the release anteriorly that weakens

the tendon. “Patellar tendon rupture is associated with previous knee surgery, knee

manipulation, and distal realignment procedures of the extensor mechanism” [20].

1.2.3.4 Vascular complications

Acute occlusive vascular problems after TKA are rare (0.03% to 0.2%). Patients with a

history of vascular disease, vascular calcification, previous vascular reconstruction, and

possibly popliteal aneurysms are at risk of an acute vascular event [25].

Direct vascular damage may occur intraoperatively, because the popliteal artery and vein,

and the tibial nerve lie close to the posterior aspect of the knee. Further, the popliteal artery

bifurcates below the level of the joint. At this point, the anterior tibial artery becomes most

at risk [25].

Arterial thrombosis after TKA is very rare but a devastating complication that frequently

results in amputation [20].

1.2.3.5 Peripheral nerve complications

Nerve injuries, especially peroneal nerve palsy, occur in 1% to 2% of patients [21]. Risk

factors for nerve injury include rheumatoid arthritis, preoperative deformity, postoperative


epidural anaesthesia, prolonged tourniquet time, and pre-existing peripheral neuropathy

[25]. To avoid nerve injury, attention to surgical detail such as careful retractor placement

and avoidance of over releasing of soft tissue and excessive polyethylene insert thickness

and care when applying dressings should be exercised [25]. When a peroneal nerve palsy is

discovered postoperatively, expectant treatment is recommended with immediate local

pressure relief and flexion of the affected knee to 20 to 30° advised [20,25].

1.2.3.6 Fractures

Periprosthetic fractures may occur around the femoral component, the tibial component, or

the patella. Reported risk factors include anterior femoral notching, osteoporosis,

rheumatoid arthritis, stiff knees, revision arthroplasty, and neurological disorders [20,31].

Femoral periprosthetic fractures are more common and occur in 2%, while the incidence of

tibial fractures is much less [32].

Function of the TKA after fracture healing depends on restoration of alignment, adequate

patellofemoral function, maintenance of prosthesis fixation, and adequate residual motion

[20].

1.2.3.7 Loss of motion

The primary goals of joint arthroplasty include pain relief and restoration of function.

Activities of daily living need a certain range of motion. For example, 70° of knee flexion

are needed to walk normally on level ground, 90° to go up most stairs, 100° to come down

those stairs, 105° to get up from most chairs, and 115° to get up from a low sofa [33,34].

Satisfactory postoperative range of motion is thus an important component of successful

total knee replacement [34]. Further, range of motion is an extremely important

determinant of patient satisfaction [35].

Postoperative stiffness is often defined by a range of motion less than 90° at six weeks

after operation. A number of factors may lead to a loss of motion after TKA, including

patient factors, preoperative ROM, prosthetic geometry, intraoperative technical errors,

knee kinematics, postoperative rehabilitation, and perioperative complications [25,36].

Patient factors predictive of stiffness include high Body Mass Index (BMI), previous knee

surgery, patients on disabilities, diabetes, depression, and pulmonary disease. Stiffness is

more common in women, and women of a younger age with a low BMI, high femoral

flexion angle, and a patella baja. Further, preoperative range of motion (ROM) influences

postoperative range [25].

Introduction - Methods to evaluate knee swelling 10

Perioperative complications, which may influence postoperative ROM, are infection,

periprosthetic fracture, component failure, complex regional pain syndrome, heterotopic

ossification, and postoperative medical complications.

Postoperative ROM may be improved by positive preoperative reinforcement, multimodal

pain management, and physiotherapy [25].

1.2.4 Postoperative swelling

Lower limb swelling occurs in most patients who undergo TKA, which can cause pain,

extended bed-rest, and a delay in rehabilitation [2]. Further, lower limb swelling may be a

warning sign of severe complications, such as DVT and infection [2]. Post-TKA limb

swelling is related to damage to blood and lymph vessels, their increased permeability,

extravasation into tissue, and the release of inflammatory factors [2].

Total knee arthroplasty requires sequential osteotomy and soft tissue release, which lead to

significant blood loss. The total blood loss is composed of ‘visible’ blood loss from the

surgical field and wound drainage, and “hidden” blood loss into the tissues [37]. Blood

retained in the joint cavity, extravasation of blood into the tissue, and haemoglobin loss

due to haemolysis contribute to hidden blood loss [2,38]. Hidden blood loss may be one of

the causes or aggravating factors of limb swelling after TKA [2].

After surgery, blood collects in the joint cavity and penetrates into the surrounding soft

tissue, increasing the circumference of the extremity in the knee region. Further, fat, bone

cement, and bone fragments may enter the circulation, leading to abnormal permeability in

the capillaries and subsequently extravasation of blood into the tissue. Extravasation into

the tissues can aggravate limb swelling [38]. As a consequence, the soft tissue around the

joint is exposed to a higher tension, which causes local pain due to pressure [2].

Current methods of reducing post-operative swelling include elevation of the affected limb

and the use of medication. Measures taken to minimize HBL could also reduce limb

swelling. These include using ice-packs or elastic bandages, intra-capsule injection of

epinephrine, restricting the drainage tube, and restoring blood volume [2].

1.3 Methods to evaluate knee swelling

A variety of methods are used to measure leg swelling. These can be subdivided into

direct, indirect and dynamic measurement methods [39]. Direct volume assessment

methods include optoelectronic measurements, computed tomography, magnetic resonance

imaging scans, and volume displacement. Indirect methods, which are most frequently

used, are based on leg circumference measurements. Dynamic measurement methods are

Introduction - Methods to evaluate knee flexion 11

based on dynamic manoevres or compression for a short period of time when using volume

plethysmography.

Currently, water displacement leg volumetry is considered to be the gold standard or

reference method [40,41]. Water displacement volumetry is based on the “Archimedes’

principle, which states that any object that is completely or partially submerged in a fluid

at rest is acted on by an upward force. The magnitude of this force is equal to the weight of

the fluid displaced by the object. The volume of fluid displaced is equal to the volume of the

portion of the object submerged” [42]. There are two major subtypes of water

displacement volumeters. The first and more common variant uses a container with an

overflow spout. Water is filled into the container until water flows from the spout.

Thereafter the patient immerses the limb into the container. The water flowing from the

spout representing the volume of the limb is weighted or its volume is measured in a

calibrated container. The second variant of water displacement volumeters measures the

level of the water in a container before and after the patient lowered the limb. The rise of

water levels is translated into volume change from a calibration curve established with

bodies of known volume [41]. Although the water displacement method is regarded as the

gold standard, it is not suitable for patients with postoperative wounds [39,43].

In general, direct and dynamic methods are expensive, cause inconvenience to patients and

are difficult to apply due to wounds and relative immobilization [39]. Preferably, a simple

and fast, but nevertheless reliable and reproducible measurement method is required for

patients who experience pain after knee surgery. Circumference measurements with

measuring tapes are easy to perform, cheap and applicable in clinical practice [39].

1.4 Methods to evaluate knee flexion

Goniometry for measuring knee range of motion (ROM) is well entrenched in the

orthopaedic field. As severe restriction in ROM has ramifications for gait, function, and the

need for manipulation, goniometry is a measure of particular importance. Furthermore,

knee flexion and extension ROMs are incorporated into orthopaedic knee scoring tools to

assess disease severity, and frequently used to assess recovery after various knee surgeries

[44].

Knee range of motion can be determined by visual estimation, universal goniometers,

digital gravity goniometers, or measurement of joint angles after X-ray visualization [45].

The choice of the appropriate instrument is based upon the purpose of the measurement

Introduction - Methods to evaluate knee flexion 12

(i.e., clinical or research), the motion being measured, and the instrument´s accuracy,

availability, cost, ease of use, and size [46].

The measured radiographic angulation between the long axis of the femur and the long axis

of the tibia is considered the gold standard for measurement of knee ROM [35,47].

The instrument most commonly used to measure range of motion in the clinical setting is

the universal goniometer, which can be used at almost all joints of the body. Universal

goniometers may be constructed of plastic or metal and are produced in many sizes and

shapes. Whatever the size or material, the basic design of every universal goniometer

includes a body and two arms - a stationary arm and a moving arm. The body resembles a

protractor and may form a half circle or a full circle. A measuring scale is located around

the body. While the scales on the half-circle goniometer read from 0 to 180° and from 180

to 0°, the scales on the full-circle models may read either from 0 to 180 degrees and from

180 to 0°, or from 0 to 360° and from 360 to 0°. The intervals on the scales may vary from

1 to 10° [46]. The stationary arm is structurally a part of the goniometer´s body and cannot

be moved independently of the body. The moving arm is attached to the fulcrum in the

centre of the body by a rivet or a screw-like device that allows the arm to move freely on

the body. The length of the goniometer´s arms varies among instruments, depending on the

size of the joints to be measured [46].

In gravity-dependent goniometers or inclinometers, the gravity´s effect on pointers and

fluid levels is used to measure joint position and motion. Gravity-dependent goniometers

are attached to or held on the distal segment of the joint to be measured. The angle between

the long axis of the distal segment and the line of gravity is noted. Although inclinometers

may be easier to use in certain situations than universal goniometers because they do not

have to be aligned with bony landmarks or centred over the axis of motion, it is critical that

the proximal segment of the joint being measured is positioned vertically or horizontally to

obtain accurate measurements. Furthermore, inclinometers are difficult to use on small

joints and on regions with soft tissue deformity or edema [46].

Electrogoniometers are used primarily in research to obtain dynamic joint measurements.

Most devices have two arms which are attached to the proximal and distal segments of the

joint being measured. The two arms are connected to a potentiometer. If the joint position

changes, the resistance in the potentiometer varies. The resulting change in voltage is used

to indicate the amount of joint motion. Electrogoniometers are expensive and their use is

time-consuming because they have to be accurately calibrated and attached to the subject.

Introduction - Methods to evaluate pain 13

Other joint measurement methods used more commonly in research setting are

radiographs, photographs, film, videotapes, and computer-assisted video motion analysis

systems [46].

Furthermore, the range of motion is often assessed by visual estimation in clinical practice

[48].

1.5 Methods to evaluate pain

There are a number of scales for evaluating pain. Among these, the Visual Analogue Scale

(VAS), Numerical Rating Scale (NRS), Verbal Rating Scale (VRS), and the Faces Pain

Scale-Revised (FPS-R) are the most commonly used measures of pain intensity in clinical

and research settings [49-51].

The VAS is a 10 cm line anchored by verbal descriptors, usually “no pain” and “worst

imaginable pain”. The patient is asked to mark the line corresponding to the intensity of

present pain. This distance from the zero anchor to the patient´s mark gives the score.

Using a millimetre scale to measure the patient´s score provides 101 levels of pain

intensity [49,50]. One of the limitations of the VAS is that it must be administered on

paper or electronically and photocopying the scale can lead to significant changes in it´s

length [50]. Because graphical orientation of the VAS may be important, both horizontal

(VAS-H) and vertical (VAS-V) orientations were employed [49]. The graphical orientation

of the VAS should be decided according to the normal reading tradition of the population

on which it is being used [50]. An advantage of the VAS is that pain is measured

continuously. However, the VAS is cumbersome to administer because it requires adequate

levels of visual acuity, motor function, and the cognitive ability to translate a sensation of

pain into a distance measure [52].

The Verbal Rating Scale (VRS) comprises a list of adjectives used to denote increasing

pain intensities. The most common words used are “no pain”, “mild pain”, and “severe or

intense pain”. For ease of recording these adjectives are assigned numbers [50]. Patients

are asked to pick the single word that best describes their current pain intensity, and their

VRS intensity level is the number associated with the word the patient chose [51]. The

VRA is ordinal [50].

A commonly used clinical measure of pain is the numerical rating scale (NRS) [50]. The

Numerical Rating Scale is an 11, 21, or 101 point scale where the end points are the

extremes of no pain and pain as bad as it could be, or worst pain. The NRS can be

graphically or verbally delivered. When presenting graphically the numbers are often

Introduction - Measurement error, Agreement and Reliability 14

enclosed in boxes and the scale is referred to as an 11 or 21 point box scale depending on

the number of levels of discrimination offered to the patient [50]. For the verbally

delivered NRS, patients are asked to indicate the intensity of pain by reporting a number

that best represents it. NRS provides interval level data [50].

Williamson and Hoggart (2005) reviewed the three pain rating scales VAS, NRS, and

VRS. They concluded that all three of the pain-rating scales are valid, reliable and

appropriate for use in clinical practice, although the VAS was the most difficult to use in

clinical practice and had the highest failure rate. Further, they stated that the NRS is

probably more useful than the VRS or the VAS as a tool for pain assessment as well as for

audit and research [50].

Figure 4: Scales to evaluate pain (VAS, NRS, VRS)

NRS Numeric Rating Scale; NRS, numerical rating scale; VDS Verbal Descriptor Scale

Source: Williamson A, Hoggart B. J Clin Nurs. 2005.[50]

1.6 Measurement error, Agreement and Reliability

1.6.1 Measurement error

No measurement is perfect. As all instruments and observers or measurers (raters) are

fallible to some extent and all humans respond with some inconsistency, any observed

score X is the sum of the true value T and an error component E (1) [53-55]:

(1)

Thus, the difference between the true value and the observed value is the measurement

error. The total error consists of systematic error and random error [53-56].


Systematic (or bias) errors are consistent, repeatable errors and refer to a general trend for

measurements to be different in a particular direction (either positive or negative) between

repeated tests. For example, there might be a trend for a retest to be higher than a prior test

due to a learning effect being present [53,56,57];.

Random (or precision) errors are inconsistent and unrepeatable and refer to sources of error

that are due to chance factors, like luck, alertness, attentiveness by the tester and normal

biological variability. Random errors increase and decrease measured scores on repeated

testing in a random manner [53,56,57].

1.6.2 Terms reproducibility, agreement, reliability and responsiveness

An essential requirement of every measuring instrument is to be valid and reproducible or

reliable. Reproducibility concerns the degree to which repeated measurements in stable

objects, e.g. subjects or patients, provide similar results [58]. The repeated measurements

may concern the same observer at different times to investigate measurement error (intra-

observer variation), or different observers to investigate the variation between them (inter-

observer variation) [59,60]. Repeated measurements may differ because of biologic

variation in subjects, e.g. in the form of day-to-day differences or a circadian rhythm.

Other sources of variation may originate from the measurement instrument itself, or the

circumstances under which the measurements take place [59].

Reproducibility is an umbrella term for the two concepts of reliability and agreement,

which are often incorrectly used interchangeably [58,59].

Measures of agreement refer to the absolute measurement error and determine the ability

of observers to achieve the same value in repeated measurements. They are expressed in

the units of the measurement, which is an important advantage for clinical interpretation

[5,59].

Measures of reliability assess the ability to differentiate among subjects in a group, despite

measurement errors, and thus refer to the relative measurement error. They provide insight

into the ability of observers to differentiate between subjects in a group. The measurement

error is related to the variability between persons. Consequently, reliability parameters are

highly dependent on the heterogeneity of the study sample, which is not the case for

agreement parameters, which are based on measurement error [5,59].

A reliability parameter has a typical basic formula (2):

(2)


Reliability relates the measurement error to the variability between study objects. The

reliability parameter approaches 1, if the measurement error is small compared to the

variability between persons. In this case the discrimination of persons is hardly affected by

measurement error, and thus the reliability is high. Conversely, if the measurement error is

large compared to the variability between persons, the reliability parameter approaches 0.

In such a case, the discrimination will be affected by the measurement error [59].

The responsiveness of a measure is the ability of the tool to detect a real change [44]. To

assess the responsiveness of an instrument, an external criterion can be used to define

whether a subject or patient has changed. The external criterion determines the minimum

change that is considered to be clinically relevant [61]. Responsiveness is strongly related

to the level of agreement [5,62].

1.6.3 Statistical Methods to assess reproducibility

A variety of statistical procedures have been proposed to assess reliability and agreement

in circumferential and goniometric measurements. These include the intraclass correlation

coefficient (ICC), the standard error of measurement (SEM), the Pearson correlation

coefficient, the coefficient of variation, and the Bland and Altman 95% limits of agreement

method (LOA) [44,45,58]. A brief review of literature for circumferential and/or

goniometric reliability studies showed, that the most common methods involve the use of

correlation coefficients (ICC, Pearson’s, Spearman) and/or hypothesis tests (ANOVA)

(Table 1). In 26 of the 30 cited articles (1976-2011), the used statistical method was a

correlation coefficient, alone, or in combination with other statistical methods. Other

methods cited in the reviewed literature involved standard error of measurement (SEM),

coefficient of variation (CV), or the Bland and Altman 95% limits of agreement (LOA).

There is no consensus regarding the appropriate statistical test in reproducibility studies of

continuous data. Several authors have discussed the inappropriateness of using tests such

as Pearson´s correlation, t-tests, coefficient of variation, per cent agreement and chi-square

[63]. De Vet pointed out that regardless of the preferred statistical methods, presenting one

single reliability coefficient is insufficient and a visual presentation of the data is advisable

[58]. Rankin and Stokes stated that the intraclass correlation coefficient and Bland and

Altman tests are appropriate and recommended the combined use for the analysis of

reliability studies [63].

Considering responsiveness, the smallest real difference (SRD) or the smallest detectable

difference (SDD) derived from reproducibility can be used to define responsiveness [61].


The following chapters will look in more detail at the intraclass correlation coefficient

(ICC) and the Bland and Altman 95% limits of agreement, which were used in the

statistical analysis.

Statistical method

Measurement study

Circumference

(n = 14)

Goniometry

(n = 18)

Circumference and goniometry

(n = 3)

Correlation coefficient ICC 7 10 2

Pearson´s 3 3

Spearman 1

CCC - 1 -

type not specified - 1 1

ANOVA 5 3 1

LOA 1 3 1

SEM 3 1 1

SDD - 1 -

SRD - - 1

CD 1 - -

CV 1 - -

CR 1 - -

RP 1 - -

Table 1: Statistical methods used in circumferential and goniometric reliability studies

Review of 11 articles for leg circumferential [39,64-73], 15 articles for knee goniometric studies [5,35,44,45,47,48,74-

82], and 4 articles for both circumferential and goniometric measurement reliability [4,83-85]; ICC; intraclass

correlation; ANOVA; analysis of variance; SEM; standard error of measurement; CV; coefficient of variation; SDD;

smallest detectable difference; SRD; smallest real difference; CD; critical difference; CR; coefficients of repeatability;

LOA; limits of agreement; RP; relative precision;

1.6.3.1 Intraclass correlation coefficient (ICC)

The ICC is defined as the ratio of the variance of interest, e.g. persons, to the total variance

(3). These variances are derived from analysis of variance (ANOVA) [57-59]. The ICC is a

measure of reliability and considers both random and systematic error, but does not allow

to discriminate between random and systematic error [45,57].

(3)


The ICC is unitless and can theoretically vary between 0.0 and 1.0. An ICC of 0 indicates

no reliability, whereas an ICC of 1 indicates perfect reliability [57]. An ICC of 0.95 means

that an estimated 95% of the observed score variance is due to true value variance [57].

Some sources have attempted to delineate good, medium, and poor levels for the ICC,

ranging from ‘questionable’ or “acceptable” (0.7 to 0.8) to ‘high’ (>0.9) [56,57,62].

Anyway, there is no consensus as to what constitutes a good ICC. This might be due to the

fact that there are six commonly used versions of the ICC and the resulting ICC value

varies depending on which version of the ICC is used [56,57].

The structure of the ANOVA model for the appropriate ICC depends on whether the

observers are drawn at random from a large population of observers (random effects) or

whether they are the only observers of interest (fixed effects), whether each observer rates

each subject or not, and whether the unit of analysis is a single observer or the mean of

several observers (Table 2) [58,86].

Furthermore, to compute an ICC with the statistical software IBM SPSS Statistics [87] or

MedCalc for Windows [88], one has to distinguish between two further types of ICCs,

ICCagreement and ICCconsistency. These differ whether or not systematic differences between

observers are taken into account (4, 5):

(4)

(5)

The variance in persons represents the variability between persons (i.e. subjects or

patients), and represents the variance due to systematic differences between observers.

In case of ICCagreement, the measurement error consists of

, while it is only

in case of ICCconsistency. The ICCagreement differs from the ICCconsistency in the extra

term in the denominator, taking into account the systematic difference between the

observers. Thus, the ICCconsistency ignores systematic differences. The specifications

“agreement” and “consistency” for the type of ICC are somewhat confusing, because both

are reliability parameters, which are dependent on the heterogeneity of the population

sample with respect to the characteristic of the study [59].

The ICC is derived from an ANOVA table, which implies that the estimation of the

reliability of ratings is based on the assumptions that the data are normally distributed and


that the variances are homogeneous between ratings [54]. The ICC includes the variance

term for individuals and is therefore dependent upon heterogeneity of the study population

[45,56,57,59]. A large ICC can mask poor trial-to-trial consistency when between-subject

variability is high. Conversely, if the between-subjects variability is low, a low ICC can be

found even when trial-to-trial variability is low [57]. Thus, a given method can have

different reliability determined from the ICC, depending on the characteristics of the

individuals included in the analysis [57]. Due to these limitations, the ICC should not be

employed as the sole statistic [56].

In addition, the ICC is a unitless ratio of variances and cannot be interpreted clinically

because it gives no indication of the magnitude of disagreement between measurements.

Therefore, it should be complemented by calculation of the standard error of measurement

(SEM) or the Bland and Altman 95% limits of agreement tests [58,63].

Observers Each subject was assessed by a

different set of randomly selected

observers

Each subject was assessed by each observer

Observers were selected at random Observers were selected

at random

Observers are the only

observers of interest

Unit of

analysis

Single rating Average

of k ratings

Single

rating

Average

of k ratings

Single

rating

Average

of k ratings

ICC type ICC(1,1) ICC(1,k) ICC(2,1) ICC(2,k) ICC(3,1) ICC(3,k)

SPSS/

Medcalc

Model

One-way random Two-way random Two-way mixed

single

measure

average

measure

single

measure

average

measure

single

measure

average

measure

Table 2: ICC types and corresponding SPSS/MedCalc model

[86]

1.6.3.2 The Bland and Altman limits of agreement

The 95% limits of agreement method proposed by Bland and Altman (1986) is based on

the mean and standard deviation (SDdiff) of the difference between two ratings of the same

subject [89]. The mean difference between two observers or measurements (mD) indicates

systematic error (or bias) and the SDdiff of the difference between two observers or

measurements indicates random error [89]. The closer mD is to zero and the smaller the

value of SDdiff, the better the agreement between measures [63]. An mD deviating

substantially from 0 indicates a systematic difference between measurements [62]. The

95% limits of agreement (LOA) are determined from mD and SDdiff (6):


(6)

Thus, the 95% limits of agreement are a measure of random (mD) error and systematic

error (1.96·SDdiff) of the measurement method. If the differences are normally distributed,

95% of the differences will lie between the limits of agreement [89]. Large limits of

agreement show poor agreement between the variables. The minimum acceptable level of

agreement depends on the clinical use and situation. It is the task of the researcher to judge,

using analytical goals, whether the limits of agreement are narrow enough for the test to be

of practical use [56,60].

To explore agreement between measurements, Bland and Altman recommended the visual

examination of data patterns with the Bland and Altman plot and quantification of the mD

between measurements and the corresponding SDdiff [90]. The Bland and Altman plot is a

scatter diagram that consists of the average of the paired values from each measurement on

the x-axis and the difference of each pair of readings on the y-axis (Figure 5). Further,

horizontal lines are drawn at the mean difference mD and at the limits of agreement

(LOA). From this graph, the size of each difference, the range of differences and their

distribution about zero, which corresponds to perfect agreement, can be seen clearly [63].

Figure 5: Example for a Bland and Altman plot

with mean difference (solid black line) and limits of agreement (broken black lines);

The presentation of the findings from the Bland and Altman limits of agreement analysis

includes the mean value of the measurement, the mean difference mD, the standard

deviation SD of the difference, and the limits of agreement (LOA). Further the Bland-

Altman plot is displayed as a graphic [57].

30 32 34 36 38 40 42 44 46

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Mean girth for Waegener tape measure (cm)

Dif

fere

nce o

bse

rver

O1-O

2 (

cm

)

Mean

0.00

-1.96 SD

-0.78

+1.96 SD

0.79

Introduction - Study hypothesis 21

From the standard deviation of the difference SDdiff, the smallest detectable difference

(SDD) can be calculated according to (7):

(7)

The smallest detectable difference (SDD) expresses the smallest difference between two

independently obtained measures that can be interpreted as “real” above measurement

error [62].

The limits of agreement depend on some assumptions about the data: The mean and the SD

are constant throughout the range of measurements and the differences are from an

approximately normal distribution. The measurements themselves do not have to follow a

normal distribution [89].

Compared to ICC, the limits of agreement do not systematically depend on the

heterogeneity of the study population. Further, it quantifies the amount of measurement

error in units of the measurement scale used, e.g. in cm or degrees. The limits of agreement

method clearly visualises systematic differences and random errors. Apart from that, it is

only minimally influenced by the number of observers for inter-observer comparisons [45].

However, the Bland and Altman 95% limits of agreement indicate a range of error, but this

must be interpreted with reference to the range of measurement values obtained. Therefore,

Bland and Altman tests should be complemented by raw data and/or ranges [63].

1.7 Study hypothesis

The first study hypothesis was that both lower extremity circumferences in the knee region

and knee flexion can be reliably assessed with the available measuring instruments.

Further, it was hypothesized that the reproducibility of circumferential measurements

depends on the measurement site and the tape measure used. Considering the measuring

tapes, it was suspected that the tension controlled tape measures would show higher

reliability and agreement than the standard tape measure.

The second study hypothesis was that the rehabilitation of in-patients undergoing TKA can

be evaluated by means of circumferential girth measurements to assess swelling,

goniometric measurements to assess ROM and the numeric rating scale to assess

postoperative pain. Further, it was hypothesised that postoperative swelling has an

influence on passive ROM.

Methods and Materials - Reliability and agreement measurements 22

2 Methods and Materials

2.1 Reliability and agreement measurements

2.1.1 Subjects and observers

Initially, twenty subjects voluntarily signed a consent form to participate in the study,

which had been approved by the ethics committee of Medical University of Graz. The

mean age of the subjects was 40.6 (range, 23-60) and 50 % were female. The mean body

mass index (BMI) was 23.20 kg/m2 (range 19.1-30.2 kg/m

2). Subjects were eligible for

participation if they gave informed consent, were between 18 and 90 years of age, had no

recent history of lower extremity pathology, BMI less than 40 kg/m2, and were able to co-

operate (e.g., no unsoundness of mind). Subjects suffering from a current fracture around

the knee, current infection or status post infection, tumour around the knee, rheumatoid

knee arthritis, any operations done around the knee except arthroscopic knee surgery, and

depression or anxiety disorder, were excluded.

The measurements were performed by five observers covering a broad spectrum of

medical and non-medical professions. Three observers had practical experience in girth

and ROM measurements (O1, O2, and O3), while the others had never before assessed

lower leg circumference with any tape measure used in this study as well as knee flexion

with a universal goniometer. Due to time constraints, only two observers (O1 and O2)

measured all 20 subjects (Table 3). The observers O3, O4, and O5 measured the same 5

subjects (subjects 5, 8, 13, 14, and 18).

Observer Sex Profession Experience Subjects measured

O1 Female Medical/engineering student yes 20

O2 Female Medical resident yes 20

O3 Male Orthopaedic surgeon yes* 5

O4 Male Engineering student no 5

O5 Female Secretary no 5

Table 3: Observers

*occasional experience with the Waegener tape measure used in the study


For girth measurements, twenty subjects were measured on the first measuring day by the

observers O1 and O2, and eighteen subjects on the second measuring day, because two

subjects did not return for their second testing (Figure 6, solid line). The sample size n was

thus 20 for the first and 18 for the second measuring days, except for Gulick I tape

measure: On the second measuring day, only 14 subjects were measured with this

measuring tape. The subjects 5, 8, 13, 14, and 18 were measured by observers O1, O2, O3,

O4, and O5 on both measuring days with all tape measures (n=5) (Figure 6, broken line).

Figure 6: Number of subjects (girth measurements)

n, sample size; GI, Gulick I tape measure; GII, Gulick II plus tape measure; S, standard tape measure; W, Waegener tape

measure

For goniometric measurements, twenty subjects were measured on the first measuring day

and eighteen subjects on the second measuring day, because two subjects did not return

(Figure 7). Accidentally, the knee flexion measurements in subject 19 were taken with the

first positioning device (2.1.3.2) on the first measuring day, and with the second

positioning device on the second measuring day. Thus, the data of subject 19 (male) was

excluded from further statistical analysis, reducing the sample size to n=19 on the first

measuring day and n=17 on the second measuring day. The subjects 5, 8, 13, 14, and 18

were measured by observers O1, O2, O3, O4, and O5 on both measuring days (n=5).


Figure 7: Number of subjects (knee flexion measurements)

2.1.2 Measuring devices

2.1.2.1 Tape measures

Four commercially available tape measuring devices were used for this study: A standard

tape measure (Prym Consumer GmbH, Stollberg, Germany), a Gulick I measuring tape

(Baseline Evaluation Instruments, Fabrication Enterprises, New York, USA), a Gulick II

plus, Model 67019 measuring tape (Country Technology, Inc., Gays Mills, USA) and a

circumference tape measure (Waegener, Beerse, Belgium). The tape portion of every

device was constructed of non-stretchable material. All measurements were recorded to the

closest 1 millimetre (mm). The measuring devices were used as recommended in the

operator´s manual, if available.

2.1.2.1.1 Standard tape measure

The standard tape measure (S) was 1.8 cm in width and 150 cm in length. The measuring

range of this tape measure was 0-150 cm (increment 0.1 cm). The scale was printed in the

direction perpendicular to the axis of the tape.

In general, the measurement obtained with an ordinary tape depends on how tightly the

tape is pulled. The harder the observer pulls the tape, the greater the tissue compression

and the smaller the measured circumference. Further, it is likely that different observers

apply a different tension on the tape.


To measure a limb girth, the standard tape measure was wrapped around the lower

extremity and positioned at the measurement site as shown in Figure 8. The observers were

advised that the tape should have contact with the skin, conform to the body surface being

measured, and not compress the underlying soft tissue.

Figure 8: Standard tape measure

2.1.2.1.2 Circumference tape measure “Waegener”

The Waegener tape measure (W) is a spring tape that was designed specifically for

circumferential measurements, as the portion of the device which contacts the skin has a

concave surface to conform to the limb´s rounded surface (Figure 9). The tape was 1.3 cm

in width and 157 cm in length with a measuring range from 0 to 150 cm (increment 0.1

cm). The scale was printed in the direction perpendicular to the axis of the tape.

The Waegener tape measure contains a spring mechanism which maintains an unknown

constant tension on the tape during measurement. This avoids the tendency to apply

different tensions on the tape at different measuring times.

Figure 9: Waegener circumferential tape measure


To take a measurement with the Waegener tape measure, the tape was pulled out of the

box and positioned around the measurement site. The pin located at the end of the tape

measure was hooked into the tape measure body forming a loop. The release button was

then pressed to tighten the tape measure around the limb with a uniform amount of tension.

The circumference was read from the ruler.

A characteristic of this device is that it enables taking measurements and recording of the

measured values by the same person. After the release button is pressed, the measuring

tape stays in place, while the observer has both hands to make adjustments and record

measurements.

2.1.2.1.3 Gulick I measurement tape

The Gulick I measurement tape (GI) was designed with a six ounce spring-loaded tension

indicator mounted at the end of the tape (Figure 10). Taking a measurement, the spring

exerts a constant, calibrated tension on the tape. According to the manufacturer, this

eliminates excessive compression of soft tissue of the limb and resulting measurement

inaccuracies.

Figure 10: Gulick I tape measure

The Gulick I measurement tape was made of non-stretchable, flexible vinyl that is 0.7 cm

in width and 150 cm in length (increment 0.1 cm) with a measuring range from 0 to 150

cm and 0 to 60 in. The scale (in cm on one side of the tape and in inches on the other side)

was printed in direction of the tape axis.

To use the Gulick I measurement tape, the tape is pulled out of the housing and wrapped

around the leg at the site to be measured. The tape’s "zero line" is aligned alongside of the

tape graduations. Then, the observer has to pull at the end of the tensioning mechanism

until the calibration mark is just seen (Figure 11). The measurement next to the tape’s

"zero line" is read.


Figure 11: Tension indicators of the Gulick I (left) and Gulick II tape measures (right)

2.1.2.1.4 Gulick II plus tape measure

The Gulick II plus tape measure (GII) consists of a non-stretch, pliable, self-retracting

fiberglass tape with both Metric (in centimetres) and English (in inches) gradations and a

tensioning device attached to the measuring tape (Figure 12). As for the Gulick I tape

measure, the tensioning device provides a known amount of tension while a measurement

is being taken and is calibrated to indicate a four-ounce tension. The Gulick II plus tape

measure is 1.5 cm in width and 305 cm in length. The measuring range is 0-305 cm and 0 –

120 in. The scale (in mm and inches on one side, in inches only on the other side) is

printed in direction of the tape axis.

To measure a leg circumference, the measuring tape is wrapped around the lower extremity

to be measured and the tape’s "zero line" (end of tape) is aligned alongside of the tape

graduations. One hand pulls at the end of the tensioning mechanism until the calibration

mark between the two red balls is just seen (Figure 11). Then the measurement is read next

to the tape’s "zero line".

Figure 12: The Gulick II plus tape measure


a 6 in = 15.24 cm, 10 in = 25.40 cm, 12 in = 30.48 cm

2.1.2.2 Universal goniometer

For the goniometric measurements, a short arm universal goniometer was used. This

goniometer type was chosen because it was thought to be the most commonly used in the

clinical setting. Further, Rothstein et al. (1983) had demonstrated that the reliability of a

small plastic goniometer with 6-ina movable arms, comparable to the one used in this

study, was as reliable as a large metal goniometer with 12-in moveable arms and a large

plastic goniometer with 10 in-movable arms [82]. The goniometer used in this study had a

scale of 360 degrees in steps of 2-degree increments and was made out of clear plastic

(Figure 13). The arms were 18 cm in length and provided a linear scale in centimetres.

Figure 13: Universal Goniometer

2.1.3 Measurement procedures

2.1.3.1 Girth measurements

The subjects were measured when relaxed and recumbent with their left and right leg in

full extension. The limbs were placed on a firm cylindrical paper roll used in hospital to

cover the examination bed. The paper roll had a diameter of 16 cm and a length of 50 cm

and was positioned under the patient´s heels of the foot (Figure 14).

In order to avoid marking the skin of the subjects, the marks for the three measurement

sites were taken on a 2.5 cm white adhesive tape. The adhesive tape ensured that the marks

would not remain on the extremity after measurement of the site. It was felt that any

residual marks might have influenced subsequent measurements.

To avoid irritation of the skin when pulling off the adhesive tape after completing the

measurements of one observer, the subjects were instructed to wear stockings usually used


in medical thrombosis prophylaxis. The adhesive tape was put on the stocking after

positioning the legs on the paper roll.

The lower extremity girth was determined by measurement of the transverse plane

circumference of the knee at mid-patellar height, as well as 7 cm below mid-patellar height

and 7 cm above mid-patellar height. The tester stood closest to the examined leg. The

patella was located by palpation, and the superior border and lower inferior pole of the

patella were marked on the adhesive tape to determine the length of the patella. The mid-

patella was then defined by dividing the length of the patella in half. Starting from the mid-

patella site a distance of 7 cm was measured to determine the measurement sites at 7 cm

proximal and distal of mid-patella.

The circumferential measurements were performed at these locations in the hope that they

would reflect changes in fluid and synovial tissue (mid-patella), muscle atrophy and fluid

in the suprapatellar pouch (7 cm above the patella) [70]. The sequence of measurements

was repeated three times at each knee by the examiner in the same order. Circumferential

measurements were recorded to the nearest 0.1 cm.

After finishing the measurements on a subject, the observer removed the adhesive tape. No

semipermanent marks were left on the stocking, so that the next examiner had to identify

the measurement site independently.

The observers measured each subject with each measuring tape at the three measurement

sites. Thus, all subjects had 36 measurements taken on the right and on the left leg during

each visit. A total of 72 measures were obtained on each leg during the first and the second

visit.

The entire examination was repeated approximately one week later on the same subjects.

Figure 14: Subject positioning for girth measurements


2.1.3.2 Goniometric measurements

To measure knee flexion, the fulcrum of the goniometer was aligned with the lateral

epicondyle of the femur (Figure 15). The stationary arm was placed parallel to the long

axis of the femur along a line extending from the greater trochanter to the lateral condyle,

and the moving arm was placed parallel to the long axis of the fibula in line with the head

of the fibula and the lateral malleolus.

Figure 15: Anatomic landmarks used for the alignment of the universal goniometer

To fix the lower extremities of the subjects in a standardised knee position, two different

custom-made devices were used (Figure 16 and Figure 17).

The first positioning device consisted of a 80 cm x 30 cm rectangular ground plate, a 30

cm x 20 cm thigh support plate, a 45 cm x 20 cm calf support plate and an 18 cm x 20 cm

foot support plate, made of spruce wood (Figure 16). The ground plate, the thigh support

plate and the calf support plate were connected to one another by hinges. On the ground

plate, two pins each were mounted at a distance of 48 cm and 59 cm from the end of the

plate. These pins served for adjusting the knee joint position, allowing the subject´s leg to

be fixed in two knee positions (P1 and P2).

Figure 16: First positioning device and subject in position P2

48 cm

59 cm

80 cm

30cm

45 cm30 cm

18 cm

Methods and Materials - Clinical course after TKA 31

For goniometric measurements, the subject´s leg was positioned on the thigh and calf

support plates as shown in Figure 16 on the right. During the measurements of the first ten

subjects, it turned out that this positioning device was only suitable for subjects with a

sufficient thigh length.

To overcome the limitations of the first positioning device, another device was constructed.

This second positioning device consisted of a 105 cm x 49 cm rectangular ground plate

made of spruce wood and three rectangular boards (1, 2, 3) mounted on the ground plate

(Figure 17). Two of these boards (1, 3) were mounted at both ends of the ground plate, and

one (2) at a distance of 70 mm from the first board (1). For goniometric measurements, the

subject was sitting in the positioning device with his/her lower back in contact with the

first board and the tip toes either in contact with the second board (flexion position P1) or

the third board (flexion position P2). Therefore, the second positioning device provided

two standardised knee joint positions.

Figure 17: Second positioning device and subject in position P2

2.2 Clinical course after TKA

2.2.1 Patients

Over a period of three months (March to July 2012) patients undergoing TKA at the

Department of Orthopaedics and Orthopaedic Surgery of the Medical University of Graz

were recruited. Twenty-nine patients voluntarily participated in the study. The patients’

clinical data such as age, gender, height, weight, body mass index (BMI) were recorded.

The mean age of patients was 69.8 (range, 50-85) and 58.6% were male (Table 4). The

mean body mass index (BMI) was 28.8 kg/m2 (range, 23.0-36.9 kg/m

2). TKA of the left

knee had been performed in 13 cases, while 16 patients had a right knee TKA.

105 cm

70 cm

49

cm

1 2 3


Patients n Mean age (range) in years Mean BMI (range) in kg/m2

Female 12 74.3 (65 to 85) 29.7 (23.0 to 36.9)

Male 17 66.6 (50 to 79) 28.1 (23.1 to 33.9)

Total 29 69.8 (50 to 85) 28.8 (23.0 to 36.9)

Table 4: Characteristics of patient sample (n=29)

n number of subjects, BMI body mass index

The criteria which were a prerequisite for inclusion in the study (inclusion criteria) or led

to exclusion from the study and from further evaluation (exclusion criteria) are listed

below (Table 5). The study was part of a larger trial approved by the ethics committee of

the Medical University of Graz.

Inclusion criteria Exclusion criteria

Sex either, age >18 and < 90 years Age < 18 or > 90 years

BMI < 40 kg/m2 BMI > 40 kg/m

2

Degenerative or posttraumatic

gonarthrosis or osteonecrosis around the

knee

Varus or valgus deformity greater than 10°, impaired extension

greater than 10°, flexion preoperative less than 90° Scheduled operation for TKA Any operations done around the knee except arthroscopic knee

surgery Patient agrees with study design, therapy

and postoperative controls

Incompliance concerning patient controlled analgesia

Education form is signed by patient and

physician

No signed education form

Current fracture around the knee, current infection or status post

infection, rheumatoid arthritis at knee, tumour around the knee

Active systemic infection (HIV, HBV, HCV)

Obstructive sleep apnea

Opioid intolerance

Circulatory disorder in the affected leg

Fibromyalgia or other chronic pain syndromes

Taking of immune modulating medication such as cortisone,

interferon or similar

Depression or anxiety disorder

Addicted to drugs or alcohol

Pregnancy or possible pregnancy without adequate

contraception

Unsoundness of mind

Table 5: Inclusion and exclusion criteria (patients)


All patients had patient-controlled analgesia (Hydromorphine) for 72 hours postoperatively

and received daily cryotherapy. Drainage was removed 48 hours after the operation. Low-

molecular-weight heparin subcutaneously was administered post-operatively for medical

thrombosis prophylaxis. In mean, the patients were discharged 8.5 (range, 6-14) days

postoperatively. The stitches were removed 2 weeks after surgery. During the in-hospital

phase patients received daily physiotherapy that consisted of active and passive

mobilisation of the knee and functional exercises including transfers from a supine position

to sitting and from sitting to standing, walking and stair climbing.

2.2.2 Data acquisition

The clinical course after TKA was evaluated by circumferential leg measurements,

measurement of knee range of motion, and recording of the NRS pain score.

The knee joint swelling after total knee replacement was evaluated by circumferential leg

measurements on the day before TKA (d-1) and every day after knee surgery until the

dismissal day. Girth measurements were taken of the involved and uninvolved legs at mid-

patella (MP), 7 cm proximal of mid-patella (MP) and 7 cm distal of mid-patella (DP). At

least two measurements were done at each measurement site, and the mean value was used

for analysis. The measuring tape used was the Waegener tape measure, whose reliability

and agreement were evaluated before in the reproducibility study. This tape measure was

chosen, because it had shown a reproducibility level comparable to the Gulick I and

standard tape measures, but was elected the most user-friendly of all tape measures

evaluated.

For the lower leg circumference measurements, patients lay supine with their knees in full

extension and lower extremity musculature relaxed. A firm cylindrical paper roll with a

diameter of 16cm and a length of 50 cm was placed underneath the heels of the foot. The

patients were told to relax their limbs. All lower extremity girth measurements were

conducted according to the described protocol.

The passive range of motion (ROM) was assessed by measurements of the maximum

passive flexion and extension possible. The ROM measurements were performed on the

day before TKA and daily from the second day after TKA (d2) until the dismissal day. The

first day after TKA (d1) was excluded from ROM measurements because of existing

drainage. The maximum passive flexion and extension was measured in supine lying

patients using the same universal goniometer that was used in the reproducibility

measurements.

Methods and Materials - Statistical methods 34

The knee pain intensity after TKA was quantified utilizing a numerical rating scale (NRS),

ranging from 1-10. The NRS score was assessed by questioning the patient concerning

maximum and minimum pain within the last twenty-four hours (“What number on a 1 to

10 scale would you give your pain when it is the worst that it gets and when it is the best

that it gets?“). The NRS score was recorded on the day before TKA and every day after

knee surgery until the dismissal day.

Measurements of circumferences and knee range of motion and recording of the pain

intensity by means of the NRS were performed by one single observer (observer O1).

Table 6 gives an overview of the performed data acquisition.

Measure d-1 d1 d2 d3 d4 d5 d6 d7

Girth x x x x x x x x

ROM x x x x x x x

NRS x x x x x x x x

Table 6: Data acquisition

2.3 Statistical methods

Statistical analyses were performed using MedCalc for Windows, version 12.7.0 (MedCalc

Software, Ostend, Belgium) [88], IBM SPSS Statistics version 20.0 (IBM Corp., Armonk,

NY, USA) [87], and Microsoft Office Excel 2010 (Microsoft, Redmond, USA) [91].

The two sources of variability examined in this study were as follows. The variability

arising when a single observer made repeated measurements around the knee on the same

subject, referred to subsequently as intra-observer repeatability. The variability arising

from differences between observers making measurements, referred to subsequently as

inter-observer repeatability.

To quantify inter-observer and intra-observer reproducibility, agreement was determined

using the Bland and Altman´s method, and reliability was assessed using the intraclass

correlation coefficient (ICC).

For agreement, the mean difference mD between two examiners (inter-observer

agreement) and between measuring days (inter-observer agreement) and the standard

deviation SDdiff of these differences was calculated. The magnitude of the SDdiff expresses

the extent to which the examiners are able to achieve the same value [5]. Subsequently, the

95% limits of agreement were calculated, defined as the mean difference between

examiners ±1.96·SDdiff of this mean difference [62]. Only differences exceeding the limits

Methods and Materials - Statistical methods 35

of agreement can be interpreted as “real” differences above measurement error [62,89].

Further, the smallest detectable difference was obtained. Because mD was unequal to zero

and thus systematic bias present, the SDD was corrected with the absolute value of mD,

extending the formula of the SDD according to (8) [45]:

| | (8)

These corrected SDDs represent the 95% threshold for change that can be detected by the

particular device beyond measurement error [45].

Although there are no clear criteria for the acceptable degree of inter- and intra-observer

agreement, differences exceeding 1 cm in case of the girth measurements and 10° in case

of the goniometric measurements were considered to be low agreement.

Further, the percentage of differences between two measurements within 1 cm in case of

the circumferential measurements and 10° in case of the flexion measurements were

calculated.

For reliability, the intraclass correlation coefficient (ICC) was derived from a two-way

random-effects analysis of variance (ANOVA), corresponding to model 2.1 according to

the guidelines specified by Shrout and Fleiss [86], for absolute agreement. The ICCs for

intra-observer reliability were calculated by comparing the first and the second

measurements taken by each observer, while the ICCs for inter-observer reliability were

calculated by comparing the measurements of each observer.

Pearson´s correlation coefficient was computed to establish a possible relationship between

circumference change and passive ROM on third (d3) and sixth (d6) postoperative day.

Here, a circumference change was defined as follows (9):

(9)

with d-1 representing the circumference measured preoperatively. A P level of 0.05 or less

was considered statistically significant.

Results - Reliability and agreement of girth measurements 36

3 Results

In this chapter, the results of the inter-observer reliability and agreement are presented for

the observers O1 and O2 on the first measuring day. The results for the second measuring

day, and for the observers O1, O2, O3, O4, and O5 who measured five subjects are

available in the appendix (A.1 and 0, respectively). Further, in order to keep the tables for

inter-observer and intra-observer agreement as simple and clear as possible, the confidence

intervals of the mean difference and of the limits of agreement are not shown in the tables

in this chapter. These may be found in the appendix as well (A.3).

3.1 Reliability and agreement of girth measurements

3.1.1 Descriptive statistics

Table 7 shows the descriptive statistics for the circumferential girth measurements of the

observers O1 and O2.

Mean girth ± SD (Range) (cm)

Observer O1 37.1 ± 2.3 (29.8 to 45.5)

O2 37.0 ± 2.3 (30.1 to 45.2)

Leg side left 37.0 ± 3.3 (29.8 to 45.4)

right 37.1 ± 3.2 (29.8 to 45.5)

Measuring day t1 37.1 ± 3.2 (29.8 to 45.5)

t2 37.0 ± 3.2 (29.8 to 45.4)

Measurement site PP 39.7 ± 2.6 (34.3 to 45.5)

MP 37.3 ± 2.1 (37.3 to 41.9)

DP 34.1 ± 2.2 (29.8 to 38.8)

Tape measure GI 36.3 ± 3.1 (29.8 to 43.1)

GII 37.6 ± 3.4 (30.7 to 45.5)

S 37.5 ± 3.3 (30.9 to 45.2)

W 36.7 ± 2.9 (30.7 to 43.4)

Table 7: Descriptive statistics for the circumference measurements

SD, standard deviation; PP, measurement site at 7 cm proximal of mid-patella; MP, measurement site at mid-patella; DP,

measurement site at 7 cm distal of mid-patella; GI, Gulick I tape measure; GII, Gulick II plus tape measure; S, standard

tape measure; W, Waegener tape measure; t1, first measuring day; t2, second measuring day;


Measured circumference differed between observers (P=0.0107), between measuring days

(P<0.0001), between leg sides (P=0.0029) and between measurement sites (P<0.0001).

There was an increase in circumference as measurements proceeded proximally. The

circumferences measured with the different tape measures showed significant differences

(P≤0.0112) between all pairs of tape measure (GI-GII, GI-S, GI-W, GII-S, GII-W, S-W).

Girth measured with the Gulick II plus and standard tape measures were in mean 0.8 to 1.3

cm larger than with the Gulick I and Waegener tape measures.

3.1.2 Inter-observer reproducibility

The results of the inter-observer agreement and reliability with regard to different

measuring positions and tape measures are presented in Table 8.

Across measuring positions and tape measures, the SDD ranged from 0.5 to 2.1 cm, and

the ICC ranged from 0.93 to 0.98.

3.1.2.1 Measurement sites

Considering the measurement sites, highest agreement was observed at the site 7 cm distal

of mid-patella (SDD range, 0.7 to 1.0 cm) followed by the mid-patella site (SDD range, 0.9

to 1.2 cm) and at the site at 7 cm proximal of mid-patella (SDD range, 0.9 to 2.1 cm).

Accordingly, reliability was slightly higher at 7 cm distal of mid-patella (ICC, 0.98) than at

mid-patella (ICC range, 0.97 to 0.98) and 7 cm proximal of mid-patella (ICC range, 0.93 to

0.98). Thus, reliability and agreement were influenced by the measurement site in the way

that both increased from proximal to distal.

3.1.2.2 Measuring tapes

Having a closer look at the different measuring tapes, the Waegener tape measure showed

highest agreement (SDD range, 0.9 to 1.0 cm), followed by the Gulick I tape measure

(range, 0.9 to 1.2 cm), and the standard tape measure (SDD range, 0.7 to 1.7 cm). The

Gulick II plus tape measure had the lowest agreement (SDD range, 1.0 to 2.1 cm).

Correspondingly, reliability was slightly higher for the Waegener tape measure (ICC 0.98)

than for the Gulick I tape measure (ICC range 0.97 to 0.98) and the standard tape measure

(range, 0.95 to 0.98). The Gulick II tape measure showed lowest reliability (ICC range,

0.93 to 0.98). Thus, the Waegener tape measure showed highest reproducibility, while the

Gulick II plus tape measure showed lowest reproducibility.


Site Tape O1 (cm) O2 (cm) Agreement: O1-O2 (cm) Reliability

Mean ± SD Mean ± SD mD ± SDdiff LOA SDD ICC [95% CI]

PP GI 39.1 ± 2.4 38.9 ± 2.5 0.2 ± 0.5 -0.9 to 1.2 1.2 0.97 [0.95 to 0.99]

GII 40.9 ± 2.5 40.5 ± 2.5 0.4 ± 0.8 -1.2 to 2.1 2.1 0.93 [0.84 to 0.97]

S 40.7 ± 2.5 40.4 ± 2.6 0.3 ± 0.7 -1.0 to 1.7 1.7 0.95 [0.89 to 0.98]

W 39.1 ± 2.4 39.1 ± 2.4 0.0 ± 0.4 -0.8 to 0.9 0.9 0.98 [0.97 to 0.99]

MP GI 36.7 ± 2.1 36.7 ± 2.0 0.0 ± 0.5 -0.9 to 1.0 1.0 0.97 [0.95 to 0.99]

GII 37.8 ± 2.2 37.8 ± 2.1 -0.1 ± 0.6 -1.2 to 1.0 1.2 0.97 [0.94 to 0.98]

S 37.8 ± 2.2 37.7 ± 2.1 0.2 ± 0.5 -0.7 to 1.1 1.1 0.97 [0.94 to 0.99]

W 37.1 ± 2.1 37.1 ± 2.0 0.0 ± 0.4 -0.8 to 0.9 0.9 0.98 [0.96 to 0.99]

DP GI 33.4 ± 2.1 33.6 ± 2.1 -0.2 ± 0.4 -0.9 to 0.5 0.9 0.98 [0.95 to 0.99]

GII 34.3 ± 2.1 34.5 ± 2.0 -0.2 ± 0.4 -1.0 to 0.6 1.0 0.98 [0.93 to 0.99]

S 34.5 ± 2.1 34.5 ± 2.0 0.0 ± 0.4 -0.7 to 0.7 0.7 0.98 [0.97 to 0.99]

W 34.1 ± 2.0 34.3 ± 2.0 -0.2 ± 0.4 -1.0 -to 0.6 1.0 0.98 [0.95 to 0.99]

Table 8: Girth - Inter-observer reproducibility for observers O1 and O2 (n=40 legs)

LOA, limits of agreement; SDD, smallest detectable difference; D ≤1cm, difference between observers O1 and O2

within 1 cm; ICC, intraclass correlation coefficient; CI, confidence interval; n, sample size

These results are displayed graphically in the form of Bland and Altman (B-A) plots for

the measurement site 7 cm proximal of mid-patella, mid-patella, and 7 cm distal of mid-

patella in Figure 18, Figure 19, and Figure 20, respectively. In these plots, each point

represents the difference between observers for each subject´s left and right lower

extremities (n=40).

For the measurement site at 7 cm proximal of mid-patella, the Bland and Altman plots

show the highest agreement for the Waegener tape measure, closely followed by the

Gulick I tape measure, while the Gulick II plus tape measure had the largest limits of

agreement (Figure 18). Further, the Gulick I and Gulick II plus tape measures show one

outlier each clearly exceeding the limits of agreement.

In case of the mid-patella measurement site, the Waegener standard tape measure

showed highest agreement, followed by the standard and GI tape measures (Figure 19).

The Gulick II plus tape measure, again, had the widest limits of agreement, even

though the limits of agreement were substantially smaller at mid-patella than at 7 cm

proximal of mid-patella. Each plot shows outliers clearly exceeding the limits of

agreement. With the Waegener tape measure, it was possible to fulfil the a priori

criterion and detect differences in girth within 1 cm (maximum SDD, 1.0 cm).


In contrast to the results at the measurement sites at 7 cm proximal of mid-patella and

mid-patella, the B-A plot of the Waegener tape measure shows larger limits of

agreement at 7 cm distal of mid-patella than the B-A plots of the other tape measures.

The B-A plots of the Gulick I and standard tape measures have the smallest limits of

agreement. Again, the plots show outliers clearly exceeding the limits of agreement.

Interpreting these results, however, one should bear in mind that the limits of agreement at

7 cm distal of mid-patella are generally smaller than at the other measurement sites. Thus,

the limits of agreement of the Waegener tape measure at 7 cm distal of mid-patella (-1.0 to

0.7 cm) are in the range of the limits of agreement measured at 7 cm proximal of mid-

patella (-0.8 to 0.9 cm) and at mid-patella (-0.8 to 0.9 cm) with this tape measure.

In summary, the level of inter-observer reproducibility depended on the measurement site

and the tape measure used. At 7 cm distal of mid-patella, all tape measures showed good

agreement. The results of the Waegener tape measure were reproducible independent of

measurement site. The reliability across measurement sites and tape measures was high

(mean 0.98).

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth GI at PP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.2

-1.96 SD

-0.9

+1.96 SD

1.2

l

r

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth GII at PP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.4

-1.96 SD

-1.2

+1.96 SD

2.1

l

r

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth S at PP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.3

-1.96 SD

-1.0

+1.96 SD

1.7

l

r

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth W at PP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.0

-1.96 SD

-0.8

+1.96 SD

0.9 l

r

Figure 18: Girth - Inter-observer B-A plots at PP for the observers O1 and O2

with mean difference between observers (solid black line) and limits of agreement (broken black lines); l, left leg; r, right

leg; The closer the limits of agreement, the higher agreement between observers for each tape measure. A mean

difference differing from zero indicates a systematic bias present.


33 35 37 39 41 43

-2

-1

0

1

2

3

Mean girth GI at MP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.0

-1.96 SD

-0.9

+1.96 SD

1.0l

r

33 35 37 39 41 43

-2

-1

0

1

2

3

Mean girth GII at MP (cm)D

iffe

ren

ce O

1-O

2 (

cm)

Mean

-0.1

-1.96 SD

-1.2

+1.96 SD

1.0l

r

33 35 37 39 41 43

-2

-1

0

1

2

3

Mean girth S at MP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.2

-1.96 SD

-0.7

+1.96 SD

1.1l

r

33 35 37 39 41 43

-2

-1

0

1

2

3

Mean girth W at MP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.0

-1.96 SD

-0.8

+1.96 SD

0.9 l

r

Figure 19: Girth - Inter-observer B-A plots at MP for the observers O1 and O2

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth GI at DP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.2

-1.96 SD

-0.9

+1.96 SD

0.5

l

r

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth GII at DP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.2

-1.96 SD

-1.0

+1.96 SD

0.6

l

r

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth S at DP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.0

-1.96 SD

-0.7

+1.96 SD

0.7 l

r

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth W at DP (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.2

-1.96 SD

-1.0

+1.96 SD

0.6l

r

Figure 20: Girth - Inter-observer B-A plots DP for the observers O1 and O2


3.1.3 Intra-observer reproducibility

The results of the intra-observer agreement and reliability of the circumferential girth

measurements for the observers O1 and O2 are presented in Table 9. Of the corresponding

Bland and Altman plots, only those for the measurement sites at 7 cm proximal of mid-

patella are shown in this chapter (Figure 22). The Bland and Altman plots for the

measurement sites at mid-patella and 7 cm distal of mid-patella are to be found in the

appendix A.1.1.2 (Figure 56, and Figure 57, respectively).

Site Tape O1

O2

mD ± SDdiff LOA SDD ICC [95% CI]

mD ± SDdiff LOA SDD ICC [95% CI]

(cm) (cm) (cm) (cm) (cm) (cm)

PP GI 0.1 ± 0.6 -1.1 to 1.3 1.3 0.97 [0.93 to 0.98] 0.1 ± 0.6 -1.2 to 1.3 1.3 0.97 [0.93 to 0.99]

GII 0.1 ± 0.8 -1.4 to 1.7 1.7 0.95 [0.90 to 0.97] -0.1 ± 0.8 -1.6 to 1.4 1.6 0.96 [0.91 to 0.98]

S 0.2 ± 0.5 -0.9 to 1.2 1.2 0.98 [0.95 to 0.99] 0.0 ± 0.6 -1.1 to 1.1 1.1 0.98 [0.95 to 0.99]

W 0.1 ± 0.5 -0.9 to 1.1 1.1 0.98 [0.96 to 0.99] 0.1 ± 0.6 -0.9 to 1.2 1.2 0.98 [0.95 to 0.99]

MP GI 0.1 ± 0.4 -0.7 to 0.9 0.9 0.98 [0.96 to 0.99] 0.0 ± 0.4 -0.8 to 0.9 0.9 0.98 [0.96 to 0.99]

GII 0.0 ± 0.5 -0.9 to 1.0 1.0 0.98 [0.95 to 0.99] 0.0 ± 0.5 -1.1 to 1.0 1.1 0.97 [0.94 to 0.98]

S 0.0 ± 0.5 -1.1 to 1.0 1.1 0.97 [0.94 to 0.98] 0.0 ± 0.4 -0.9 to 0.9 0.9 0.98 [0.96 to 0.99]

W 0.0 ± 0.5 -1.0 to 1.0 1.0 0.97 [0.94 to 0.99] 0.1 ± 0.4 -0.8 to 0.9 0.9 0.98 [0.96 to 0.99]

DP GI 0.1 ± 0.5 -0.8 to 1.1 1.1 0.98 [0.95 to 0.99] 0.2 ± 0.4 -0.6 to 1.0 1.0 0.98 [0.94 to 0.99]

GII 0.1 ± 0.5 -0.9 to 1.2 1.2 0.97 [0.94 to 0.98] 0.2 ± 0.5 -0.8 to 1.3 1.3 0.97 [0.92 to 0.98]

S 0.0 ± 0.5 -0.9 to 1.0 1.0 0.98 [0.95 to 0.99] 0.2 ± 0.4 -0.7 to 1.0 1.0 0.98 [0.95 to 0.99]

W 0.1 ± 0.5 -0.8 to 1.1 1.1 0.97 [0.95 to 0.99] 0.1 ± 0.5 -0.8 to 1.1 1.1 0.97 [0.95 to 0.99]

Table 9: Girth - Intra-observer reproducibility for observers O1 and O2

3.1.3.1 Observer O1

For observer O1, the SDD ranged from 0.9 to 1.7 cm across the three measurement sites

and four tape measures (Table 9). The ICC ranged from 0.95 to 0.98.

Considering the different measurement sites, agreement was higher at mid-patella

(SDD range, 0.9 to 1.0 cm) than at 7 cm distal of mid-patella (SDD range, 1.0 to 1.2

cm). As for inter-observer agreement, the intra-observer agreement was lowest at 7 cm

proximal of mid-patella (SDD range, 1.1 to 1.7 cm). Accordingly, reliability was

higher at mid-patella and 7 cm distal of mid-patella (ICC range, 0.97 to 0.98) than at 7


cm proximal of mid-patella (ICC range, 0.95 to 0.98. Thus, the measurement site at 7

cm proximal of mid-patella showed the lowest level of intra-observer reproducibility.

Taking a closer look at the different measuring tapes, highest agreement was found for

the Waegener tape measure (SDD range, 1.0 to 1.1 cm), followed by the standard tape

measure (SDD range, 1.0 to 1.2 cm) and the Gulick I tape measure (SDD range, 0.9 to

1.3 cm). Again, the Gulick II plus tape measure showed lowest agreement (SDD range,

1.0 to 1.7 cm). Accordingly, reliability was higher for the Gulick I, and standard tape

and Waegener tape measures (ICC range, 0.97 to 0.98) than for the Gulick II plus tape

measure (ICC range, 0.95 to 0.97). Thus, intra-observer reproducibility was lowest for

the Gulick II plus tape.

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3

Mean girth GI at PP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-1.1

+1.96 SD

1.3

l

r

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3

Mean girth GII at PP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-1.4

+1.96 SD

1.7

l

r

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3

Mean girth S at PP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.9

+1.96 SD

1.2

l

r

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3

Mean girth W at PP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.9

+1.96 SD

1.1l

r

Figure 21: Girth - Intra-observer B-A plots at PP for the observers O2

3.1.3.2 Observer O2

Observer O2 showed slightly higher level of reproducibility than observer O1 (SDD range,

0.9 to 1.6 cm and ICC range, 0.96 to 0.98).

Considering measurement sites, reproducibility was higher at the mid-patella site (SDD

range, 0.9 to1.1 cm and ICC range, 0.97 to 0.98) than at 7 cm distal of mid-patella


(SDD range, 1.0 to 1.3 cm and ICC range, 0.97 to 0.98) and 7 cm proximal of mid-

patella (SDD range, 1.1 to 1.6 cm and ICC range, 0.96 to 0.98).

Observer O2 performed most reproducible with the standard tape measure (SDD range,

0.9 to 1.1 cm and ICC 0.98), followed by the Waegener tape measure (SDD range, 0.9

to 1.2 cm and ICC range, 0.97 to 0.98) and the Gulick I tape measure (SDD range, 0.9

to 1.3 cm and ICC range, 0.97 to 0.98). Again, the Gulick II plus provided least

reproducible results (SDD range, 1.1 to 1.6 cm and ICC range, 0.96 to 0.97).

Summarising these results, the level of intra-observer reproducibility depended on the

measurement site and the tape measure used. Both observers performed the 'least best' at 7

cm proximal of mid-patella and with the Gulick II plus tape measure. Observers were not

able to fulfil the a priori criterion (difference between measuring days ≤1cm) with neither

tape measure.

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-1.2

+1.96 SD

1.3

l

r

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

-0.1

-1.96 SD

-1.6

+1.96 SD

1.4

l

r

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

-0.0

-1.96 SD

-1.1

+1.96 SD

1.1l

r

33 35 37 39 41 43 45 47

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.9

+1.96 SD

1.2

l

r

Figure 22: Girth - Intra-observer B-A plots at PP for the observers O2

Results - Reliability and agreement of knee flexion measurements 44

3.2 Reliability and agreement of knee flexion measurements

3.2.1 Descriptive statistics

Table 7 shows the descriptive statistics of the goniometric measurements for the observers

O1 and O2 and both legs. Flexion values were comparable between observers (P=0.1344)

and leg sites (P=0.1020). Mean flexion was higher on second measuring day than on first

measuring day (P<0.0001). Further, mean flexion values in test position P1 were higher

than in test position P2 (P<0.0001). For further analysis, both legs were considered as

independent entities.

Mean flexion ± SD (Range) (°)

Measuring day

t1

97.0 ± 12.7 (64.0 to 134.5)

t2

98.9 ± 19.7 (68.0 to 138.0)

Leg side

left

97.9 ± 19.9 (64.0 to 138.0)

right

98.2 ± 19.5 (64.0 to 138.1)

Observer

O1

98.3 ± 20.3 (64.0 to 138.0)

O2

97.9 ± 19.1 (70.0 to 132.0)

Test position

P1

112.4 ± 17.5 (90.0 to 138.0)

P2

83.7 ± 7.6 (64.0 to 102.0)

Table 10: Descriptive statistics for the goniometric measurements

3.2.2 Inter-observer reproducibility

Table 11 summarizes the results of the inter-observer reliability and agreement analysis for

the observers O1 and O2 and 19 subjects. Figure 23 shows the corresponding Bland and

Altman plots.

Position O1 O2 Agreement: O1-O2 Reliability

Mean ± SD (°) Mean ± SD (°) mD ± SDdiff (°) LOA (°) SDD (°) ICC [95% CI]

P1 112.0 ± 18.1 111.1 ± 17.1 1.0 ± 2.5 -4.0 to 5.9 5.9 0.99 [0.98 to 0.99]

P2 82.4 ± 8.3 85.1 ± 8.8 -1.1 ± 3.6 -8.2 to 6.0 8.2 0.88 [0.77 to 0.93]

Table 11: Flexion – Inter-observer reproducibility for observers O1 and O2 (n=38 legs)

P1, first position; P2, second position


The SDD ranged from 5.9 to 8.2°, and the ICCs ranged from 0.88 to 0.99. Considering the

different measuring positions, inter-observer agreement was higher for knee position P1

than for P2. This was also reflected by the ICC, which was 0.99 for knee position P1, and

0.88 for knee position P2. Accordingly, the Bland and Altman plots in Figure 23, show

smaller limits of agreement for knee position P1. Further, there is an outlier exceeding a

mean difference of 10° for test position P2.

80 90 100 110 120 130 140 150

-15

-10

-5

0

5

10

15

Mean flexion at P1 (°)

Dif

fere

nce

O1

-O2

(°)

Mean

1.0

-1.96 SD

-4.0

+1.96 SD

5.9

l

r

65 70 75 80 85 90 95 100 105

-15

-10

-5

0

5

10

15


Dif

fere

nce

O1

-O2

(°)

Mean

-1.1

-1.96 SD

-8.2

+1.96 SD

6.0

l

r

Figure 23: Flexion - Inter-observer B-A plots for the observers O1 and O2

with mean difference between observers (solid black line) and limits of agreement (broken black lines);

3.2.3 Intra-observer reproducibility

Table 12 summarizes the intra-observer agreement and reliability of knee flexion

measurements for the observer O1 and O2. Figure 24 shows the corresponding Bland and

Altman plots.

The SDD ranged from 7.1° to 8.1°, and the ICC ranged from 0.87 to 0.99. Considering the

different positions, there was hardly any difference in agreement between knee position P1

and P2 (SDD range, 7.1 to 8.1° and 7.2 to 7.7°. However, reliability was higher for

position P1 than P2 (0.98, and range, 0.87 to 0.90, respectively).

Having a closer look at differences in agreement between the observers O1 and O2 shows

that observer O1 had slightly smaller SDDs than observer O2 (range, 7.1 to 7.7°, and 7.2 to

8.1°, respectively). This was also reflected by the ICC values, which were slightly higher

for observer O1 than O2 (range, 0.90 to 0.98, and 0.87 to 0.98, respectively).

Comparing the SDD values with the ICC values in Table 12 shows that there are certain

inconsistencies in the statistical results. The lowest agreement was found for observer O2

at right knee position P1 (SDD 8.1°). However, the corresponding ICC value was 0.98,

suggesting high reliability. In contrary, the second lowest agreement was found at left knee


position P2 for observer O1 (SDD 7.7 °). In this case, the ICC was 0.90, which appears to

be a reasonable value. These unexpected results will be considered in more detail in the

discussion chapter (4.3).

Position O1 O2

mD ± SDdiff LOA SDD ICC [95% CI] mD ± SDdiff LOA SDD ICC [95% CI]

(°) (°) (°) (°) (°) (°)

P1 -1.8 ± 2.7 -7.1 to 3.6 7.1 0.98 [0.95 to 0.99] -1.9 ± 3.2 -8.1 to 4.3 8.1 0.98 [0.93 to 0.99]

P2 -3.2 ± 2.3 -7.7 to 1.2 7.7 0.90 [0.15 to 0.97] -0.8 ± 3.3 -7.1 to 5.6 7.1 0.87 [0.76 to 0.93]

Table 12: Flexion – Intra-observer reproducibility for observers O1 and O2 (n=34 legs)

Another interesting fact is that the mean difference between measuring days was negative

for both observers. This negative mean difference suggests that both observers measured

higher flexion values on the second measuring day.

80 90 100 110 120 130 140 150

-10

-5

0

5

10

Mean flexion at P1 (O1) (°)

Dif

fere

nce

t1

-t2

(°)

Mean

-1.8

-1.96 SD

-7.1

+1.96 SD

3.5

l

r

80 90 100 110 120 130 140 150

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-1.9

-1.96 SD

-8.1

+1.96 SD

4.3

l

r

60 70 80 90 100 110

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-3.2

-1.96 SD

-7.7

+1.96 SD

1.2 l

r

60 65 70 75 80 85 90 95 100 105 110

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-0.8

-1.96 SD

-7.1

+1.96 SD

5.6

l

r

Figure 24: Flexion - Intra-observer B-A plots for the observers O1 and O2

at knee positions P1 and P2 with mean difference (solid black line) and limits of agreement (broken black lines)

Results - Clinical Course after TKA 47

In summary, the intra-observer reproducibility was low or, at best, acceptable. However,

the differences between measurements did not exceed the a priori criterion of 10°. The

statistical measures ICC and SDD showed inconsistencies, which have to be further

discussed (4.3).

3.3 Clinical Course after TKA

In this chapter, the presented results refer to mean values obtained from the data of 29

patients evaluated for changes in girth, passive ROM and NRS.

3.3.1 Changes in lower limb girth

Figure 25 shows the chronological course of the lower extremity girth after TKA surgery at

the three measurement sites 7 cm proximal of mid-patella (PP), mid-patella (MP) and 7 cm

distal of mid-patella (DP) of the operated lower extremity.

After operation, there was an increase of girth at all measurement sites. The site 7 cm

proximal of mid-patella showed the highest increase in girth, with in mean 5.1 cm (range,

2.3 to 7.6 cm). The mean increase at the mid-patella site and at 7 cm distal of midpatella

was smaller (3.8 cm, range, 1.9 to 9.8 cm, and 2.8 cm, range, 1.7 to 7.2 cm, respectively).

Figure 25: Changes in mean girth of the operated lower leg

at the three measurement sites; PP, 7 cm proximal of mid-patella; MP, mid-patella; DP, 7 cm distal of mid-patella

For the measurement sites 7 cm proximal and distal of mid-patella, the maximum girth was

reached 4.0 days after surgery (range, 2 to 11 days), and slightly earlier at mid-patella

(mean 3.6 days after TKA, range, 1 to 11 days). In one patient, the maximum girth was

measured on the dismissal day, thus one can not be sure if this was the maximum, actually.

36

38

40

42

44

46

48

-1 1 2 3 4 5 6 7

Mea

n G

irth

(cm

)

Days after TKA

PP

MP

DP


Excluding this patient from analysis, the maximum girth was reached earlier (mean 3.7, 3.4

and 3.8 days after TKA for PP, MP, and DP, respectively).

Figure 26 shows the chronological lower extremtity circumference change of the operated

leg (OP) and the contralateral, uninvolved leg (CL) for the three different mesasuring sites.

It can be seen that not only the girth of the operated leg, but also the girth of the

uninvolved leg showed changes in girth over time. The circumference of the uninvolved

leg showed a decrease during hospitalisation. Taking a closer look at the mid-patella site,

the course of the curves of the operated and the contralateral leg seem to be similar, having

peaks at the same timepoints of the x-axis. In the girth curves at 7 cm proximal and distal

of mid-patella, this course was only indicated by a small peak on the second postoperative

day.

Figure 26: Changes in mean girth of the operated and the contralateral leg

OP, operated leg; CL, contralateral leg

38

40

42

44

46

48

-1 1 2 3 4 5 6 7

Mea

n g

irth

at

PP

(cm

)

Days after TKA

OP CL

38

40

42

44

46

-1 1 2 3 4 5 6 7

Mea

n g

irth

at

MP

(cm

)

Days after TKA

OP CL

32

34

36

38

40

42

-1 1 2 3 4 5 6 7

Mea

n g

irth

at

DP

(cm

)

Days after TKA

OP CL


3.3.2 Changes in passive range of motion

The postoperative change of passive knee ROM after TKA surgery is shown in Figure 27.

After surgery, the mean passive knee ROM decreases from 117.1° (range, 80 to 135°)

preoperatively to 54.5° (range, 30 to 75°) on the second postoperative day. However,

during hospital stay, the mean passive ROM increases again from day to day, reaching

79.0° (range, 55 to 100°) on the sixth day after TKA operation.

Figure 27: Changes in mean passive ROM

ROM, range of motion

3.3.3 Changes in pain intensity (NRS)

Figure 28 shows the chronological changes in minimum and maximum pain in the form of

the NRS reported by the patients.

Interestingly, the maximum pain was stated preoperatively (mean 7.0, range 4 to 9), and

not, as was expected, postoperatively. The reason for this might be the fact that all patients

had patient-controlled analgesia for 72 hours postoperatively. Further, pain is a primary

indication for TKA, while pain release is a primary goal.

After surgery, the maximum pain decreased from the first postoperative day (mean NRS

6.6, range, 3 to 9) to the dismissal day (mean NRS 3.0, range 1 to 9). The minimum NRS

curve showed a similar course as the maximum NRS curve, except for a very small

increase on the first postoperative day, indicating that the minimum pain increased for a

short period after surgery.

0

20

40

60

80

100

120

140

-1 2 3 4 5 6 7

Mea

n p

ass

ive

RO

M (

°)

Days after TKA


Figure 28: Changes in mean minimum and maximum NRS

NRS, numerical rating scale;

3.3.4 Relationship between girth, ROM and pain changes

In the following figures, the changes in girth and passive ROM (Figure 29), girth and NRS

pain scale (Figure 30), and passive ROM and reported NRS pain scale (Figure 31) are

compared. Because the lower leg circumferences at the different measurement sites

changed in a similar way, only the results of the measurement site at 7 cm proximal of

mid-patella will be presented in this chapter. Figures comparing the circumferential

changes at mid-patella and at 7 cm distal of mid-patella with passive ROM and the NRS

are to be found in the appendix (A.4).

Figure 29: Clinical course - Girth at PP and passive ROM

1

2

3

4

5

6

7

8

9

10

-1 1 2 3 4 5 6 7

Mea

n N

RS

Days after TKA

Maximum NRS Minimum NRS

0

20

40

60

80

100

120

140

35

37

39

41

43

45

47

49

-1 1 2 3 4 5 6 7

Pa

ssiv

e R

OM

(°)

Gir

th (

cm)

Days after TKA

Mean girth at PP Mean passive ROM


A comparison of girth at 7 cm proximal of mid-patella and the passive ROM showed an

opposite course of the curves (Figure 29). Girth increased up to a maximum on the third

postoperative day, from which it decreased slowly until the dismissal day. The passive

ROM first decreased after surgery, but kept increasing in the course of inpatient stay.

Figure 30 shows the course of girth and mean maximum reported NRS. On the fifth

postoperative day, there was a small peak in the NRS curve. The girth curve showed a

corresponding slower decrease on the same day.

Figure 30: Clinical course - Girth at PP and maximum reported NRS

The curves of the passive ROM and reported NRS are compared in Figure 31. While the

reported NRS kept decreasing from the beginning, the passive ROM kept increasing.

Figure 31: Clinical course – Passive ROM and maximum NRS

1

2

3

4

5

6

7

8

9

10

35

37

39

41

43

45

47

-1 1 2 3 4 5 6 7

Ma

xim

um

NR

S

Gir

th [

cm]

Days after TKA

Mean girth at PP Mean NRSmax

1

3

5

7

9

0

20

40

60

80

100

120

140

-1 1 2 3 4 5 6 7

Ma

xim

um

NR

S

Pa

ssiv

e R

OM

(°)

Days after TKA

Mean passive ROM Mean NRSmax


The Pearson´s correlation coefficient between the circumference change on the third and

sixth postoperative and the corresponding passive ROM showed no significant correlation

between swelling and passive ROM (P≥0.1375).

3.3.5 Postoperative follow up examination six weeks after TKA

Girth measurements of the operated leg and passive ROM measurements were performed

in 10 of the 29 patients during six weeks follow up check. Table 13 shows the differences

in girth and passive ROM between this postoperative 6-weeks check and the day of

dismissal (“6 weeks-dismissal”). Further, the girth and ROM values were compared to

those obtained preoperatively (“preoperative - 6 weeks check”).

Patient No. Difference (6 weeks check - dismissal) Difference (preoperative – 6 weeks check)

Girth (cm) PROM (°) Girth (cm) PROM (°)

PP MP DP

PP MP DP

2 0.1 -0.5 0.2 25 0.4 1.9 1.2 -14

5 -2.5 -1.3 -1.3 -5 2.0 0.8 2.2 -42

8 -0.5 0.5 -0.9 25 1.7 2.1 2.3 -15

11 -7.1 -4.6 -5.1 30 2.1 0.9 0.6 -6

14 -3.3 -1.3 -1.9 15 1.5 -0.4 1.0 -19

17 -2.8 -2.4 -1.7 20 2.1 0.8 0.8 -21

19 -1.3 0.1 -0.7 35 1.9 1.4 0.9 3

22 -2.4 -1.5 -0.1 30 3.3 4.2 3.6 -13

24 -1.2 -3.7 0.2 55 -0.2 -2.8 0.6 14

29 0.4 1.0 1.0 25 3.4 2.6 1.4 -13

Table 13: 6-weeks check: Changes in girth and PROM

compared to day of dismissal and compared to values obtained preoperatively; PROM;, passive range of motion;

There was a mean decrease in girth of -2.1 cm (range, -7.1 to 0.4 cm) at 7 cm proximal of

mid-patella, -1.4 cm (range, -4.6 to 1.0 cm) at mid-patella, and -1.0 cm (range, -5.1 to 1.0

cm) at 7 cm distal of mid-patella between the day of dismissal and the six weeks check.

The passive ROM showed a mean increase of 25.5° (range, -5 to 35°). Considering the

values presented above, the negative values mean a decrease, while the positive values

mean an increase in girth or passive ROM. Thus, neither did swelling decrease in all

patients examined, nor passive ROM increase. Table 13 further shows that the lower

extremity circumferences were higher at the six weeks follow-up check than preoperatively


in most of the cases, suggesting that there was still swelling present six weeks after

surgery. Comparing the passive ROM before surgery and six weeks after, it is seen that

patients did not reach preoperative passive ROM within six weeks postoperatively (mean -

2.1, range -7.1 to 0.4 °), except for two patients (patient No. 2 and patient No. 29).

3.3.6 Influence of gender and BMI on postoperative swelling

To consider a possible influence of the BMI on limb swelling after TKA, the patients were

divided into BMI <30 kg/m2

and a group with BMI ≥30 kg/m2

groups. Ten of the 29

patients (34%) had a BMI ≥30 kg/m2. The results of the comparisons in Table 14 show that

patients with a BMI less than 30 kg/m2

reached the maximum girth earlier than adipose

patients. At 7 cm proximal of mid-patella, there was no difference in maximum swelling,

which was defined as the difference of maximum girth and minimum girth, i.e.

preoperatively. However, at mid-patella and 7 cm distal of mid-patella, the maximum

swelling was higher for the adipose group.

Having a closer look at possibly existing differences due to gender, the results of female

patients were compared with those of male patients. Male patients reached the maximum

swelling earlier than the females (Table 14). Further, at mid-patella and 7 cm distal of mid-

patella, female patients showed higher maximum swelling.

Factor Day of maximum swelling Mean maximum swelling (cm)

PP (range) MP (range) DP (range) PP (range) MP (range) DP (range)

BMI (kg/m2) <30 3.8 (2-6) 3.5 (1-8) 3.8 (2-8) 5.1 (2.6-7.6) 3.4 (1.9-5.3) 3.6 (1.7-5.4)

≥30 4.4 (2-11) 3.8 (2-11) 4.4 (2-11) 5.1 (2.3-7.2) 4.4 (2.1-9.8) 4.0 (1.8-7.2)

Gender f 4.4 (2-11) 3.7 (1-11) 4.3 (3-11) 5.0 (2.3-7.0) 4.3 (2.4-9.8) 3.9 (1.8-7.2)

m 3.7 (2-6) 3.6 (2-8) 3.8 (2-8) 5.2 (2.6-7.6) 3.4 (1.9-5.6) 3.6 (1.7-5.4)

Table 14: Effects of BMI and gender on lower extremity swelling after TKA

Maximum swelling = Difference of maximum girth and minimum girth; f, female; m, male;

Summarizing these results, one could speculate that the BMI and the sex have an influence

on postoperative swelling. However, taking a closer look at the sex distribution in the BMI

groups, it shows that in the adipose group there are six females and four males, while in the

group with BMI <30 kg/m2 there are thirteen males and six females. For this reason, the

sex related differences sex might be due to the fact that more female than male patients in

the study population were adipose. Further, a statistical analysis of these data with


appropriate methods would be necessary in order to make a statement on the impact of

gender and BMI on postoperative swelling.

3.3.7 Subjective judgment of knee swelling vs. girth measurements

Questions concerning an existing swelling are included in many outcome questionnaires,

e.g., the Knee Injury and Osteoarthritis Outcome Score (KOOS), Lysholm Knee Scoring

Scale, and the Knee Outcome Survey - Activities of Daily Living (KOS-ADL). In the

course of data acquisition in this study the question arose whether patients are able to

assess changes in postoperative swelling. Therefore, patients were asked if the swelling in

the knee region had increased or decreased within the last 24 hours prior to the knee girth

measurements. These answers were compared with the results of the girth measurements at

the mid-patella measurement site according to (10):

(10)

Only differences in girth of 0.5 cm or greater were considered real changes in swelling. “I

don´t know” answers were excluded. A total of 70 patient answers were analysed. The

results showed that the subjective judgment of the patients regarding knee swelling and the

measurement results did only agree in 49%. In other words, in more than half of the cases,

patients were not able to properly assess changes in knee swelling. One patient even

reported no swelling although there was an increase in girth of 2.8 cm at 7 cm proximal of

mid-patella, 1.3 cm at mid-patella, and 1.0 cm at 7 cm distal of mid-patella, compared with

the preoperative circumference values.

Figure 32: Subjective judgment of swelling in the knee region by patients

48,6% 51,4%

Subjective judgment of swelling by patients

correct incorrect

Discussion - Discussion of the girth reproducibility measurements 55

4 Discussion

The primary purpose of this study was to evaluate the reliability and reproducibility of

circumferential tape measurements with four different types of tape measures using intra-

and inter-observer coefficients. The secondary purpose was to describe the clinical course

of the swelling in the knee joint region/area after/following total knee arthroplasty. The

main findings of this study were

1) The level of reproducibility of circumferential measurements differed substantially

dependent on the measuring position and tape measure used. With the Waegener

tape measure, differences in girth exceeding 1.2 cm can be considered a real change

above measurement error;

2) Knee flexion changes above 9° seems to detect a real change;

3) After TKA, swelling in the knee region was observed in all patients, being highest

at 7 cm proximal of mid-patella. Mean passive ROM on the day of dismissal was

81.7°. Reported pain intensity was highest preoperatively.

4.1 Discussion of the girth reproducibility measurements

4.1.1 Discussion of the results

Based on the results of inter- and intra-observer agreement, the smallest detectable

differences would lie between 0.4 cm and 2.1 cm, clearly exceeding the a priori criterion of

1 cm. Inter-observer agreement was slightly higher for the second measuring day. Further,

observers O1 and O2 showed comparable results in intra-observer comparisons. Reliability

was generally high, with ICC values ranging from 0.93 to 0.99.

Measurements SDD (cm) ICC

total 0.7 to 2.1 0.93 to 0.99

t1: O1-O2 0.7 to 2.1 0.93 to 0.98

t2: O1-O2 0.7 to 1.8 0.94 to 0.99

O1: t1-t2 0.9 to 1.7 0.95 to 0.98

O2: t1-t2 0.9 to 1.6 0.96 to 0.98

Table 15: Girth - Summary of the results (observers O1 and O2)


Intra-tester reproducibility for observers O1 and O2 was higher than inter-tester

reproducibility. This is in agreement to previous reports on circumferential measurements

of the lower extremity [39,67,72,92], which found higher intra-observer reliability than

inter-observer reliability.

In literature, there is no agreement on reproducibility of lower extremity circumference

measurements with tape measures. Whitney et al. (1995) stated that girth measurements in

the clinic can be highly repeatable (ICC 0.91 to 1.00) in experienced clinicians by using a

simple standardized procedure [73]. In their study, girth of thirty subjects was assessed at

five different lower extremity sites by two experienced physical therapists with a standard

tape measure. Harrelson et al. (1998) performed lower extremity circumference

measurements in twenty-one subjects at three measurement sites with a standard tape

measure and a Lufkin tape measure with a Gulick spring-loaded handle attached and

reported high reliability (ICC 0.98 to 0.99) [67]. Others evaluated circumferential

measurements of the involved and uninvolved legs in nine patients recovering from

anterior cruciate ligament reconstructive surgery [72]. They stated that “the measurements

established sufficiently high reliability to justify their use both within and between

examiners for subjects recovering from surgery of the anterior cruciate ligament” (ICC

0.82 to 1.0 and 0.72 to 0.97, respectively). This is in agreement with te Slaa et al. (2011),

who concluded that “tape measurements have been proved to be a reliable and

reproducible method to assess the lower limb circumference” [39]. Jakobsen et al (2010)

examined 19 outpatients having received a TKA reported that circumference

measurements were generally reliable (ICC 0.98 to 0.99) and that changes in “knee joint

circumference of more than 1.0 cm and 1.63 cm represent a real clinical improvement

(SRD) or deterioration for a single individual within and between physiotherapists,

respectively” [4].

Maylia et al. (1999), in contrast, stated that the degree of inaccuracy of tape measurements

of the thigh is sufficient to indicate that it is of little value in the assessment of the lower

limb. They concluded that the technique is not a reliable method of monitoring the

rehabilitation of a patient [93].

The results vary considerably across studies and estimates are difficult to compare due to

differences in study design, subject groups, observers, and measurement methods.

4.1.1.1 A priori criterion

Prior to the study, the maximum clinically acceptable SDD was set 1 cm for girth

measurements, because it was felt that a change in girth of 1 cm would be clinically


relevant and should thus be detectable. The results show that the SDD in part exceeded this

a priori criterion for all measurement sites and all measuring tapes. Table 16 shows the

percentage of differences between observers and between measuring days exceeding 1 cm,

1.5 cm and 2 cm, respectively, for all measurement sites and tape measures.

Nicholas et al. (1976) stated that a change in circumference noted by different observers on

two different days was significant if it exceeds 1.5 cm at mid-patella, 2.7 cm at 7 cm

above, and 3.5 cm at 15 cm above the patella [70]. Further they reported that the change

needed to exceed only 1.0, 2.0, and 2.7 cm, respectively, to be significant if a single

observer performed both measurements [70]. Thus, the a priori criterion might have been

set at an unrealistic low level.

Tape D >1.0 cm [%] D >1.5 cm [%] D >2.0 cm [%]

PP MP DP PP MP DP PP MP DP

Inter-observer O1-O2 GI 7.4 4.4 1.5 0.0 0.0 0.0 0.0 0.0 0.0

GII 19.7 5.3 2.6 6.6 1.3 0.0 3.9 0.0 0.0

S 13.2 1.3 1.3 1.3 0.0 0.0 0.0 0.0 0.0

W 0.0 1.3 1.3 0.0 0.0 0.0 0.0 0.0 0.0

Intra-observer t1-t2 GI 10.7 1.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0

GII 19.4 4.2 2.8 4.2 0.0 0.0 0.0 0.0 0.0

S 6.9 5.6 2.8 0.0 0.0 0.0 0.0 0.0 0.0

W 4.2 5.6 4.2 2.8 0.0 1.4 0.0 0.0 0.0

Table 16: Girth - Inter-observer reproducibility for observers O1 and O2 (n=40 legs)

D >1.0 cm/>1.5 cm/>2.0 cm, difference between measurements exceeding 1.0 cm /1.5 cm/2.0 cm, difference between

measurements exceeding;

4.1.1.2 Location of measurement

In this study, the different measurement sites influenced reproducibility. The lowest level

of agreement was found for the measurement site at 7 cm proximal of mid-patella

(maximum SDD 2.1 cm). The measurement sites at mid-patella and 7 cm distal of mid-

patella showed higher agreement both within and between observers with maximum SDD

values of 1.1 cm and 1.3 cm, respectively. This was confirmed by greater ICCs for both

inter-tester and intra-tester variation at the sites mid-patella and 7 cm distal of mid-patella

compared to the site at 7 cm proximal of mid-patella.

These results are in agreement with the findings of Nicholas et al. (1976) who performed

measurements of the circumference of the knee with an ordinary tape measure at mid-


patella, 7 cm above the superior border of the patella, and 15 cm above the superior border

of the patella. They reported that intra-observer and inter-observer variations were smallest

at the mid-patella and increased as the location of measurement moved from the mid-

patella to 7 and 15 cm above the superior border of the patella. They stated that this

observation was probably due to the cylindrical shape of the thigh, since the circumference

of a cone varies significantly as one moves along the long axis [70]. Kirwan et al. (1979)

and Soderberg et al. (1996) noted variations by site of measurement. Kirwan et al. (1979)

made girth measurements with “tape measures available in hospital” at the mid-patella

level and at 1 cm and 15 cm above the palpated upper boarder of the patella [68]. They

stated that the circumference 1 cm above the patella could be measured “most precisely” of

the three circumferences tested. In the study of Soderberg et al. (1996), circumferential

measurements of the uninvolved and involved legs in patients recovering from anterior

cruciate ligament reconstructive surgery were taken at 15 cm inferior to the joint line, 5

cm, 10 cm, and 15 cm superior to the joint line, and at mid-thigh with a specially designed

device. They reported that correlation coefficients (ICC) were lowest for the joint line [72].

Inter-observer reproducibility was higher than intra-observer reproducibility for the

measurement site at 7 cm distal of mid-patella and for the Gulick I and Waegener tape

measures. This is in contradiction to previous reports on circumferential measurements of

the knee joint region, which observed higher intra-observer reliability and/or agreement

[4,39,66,68,70,72,84].

4.1.1.3 Tape measures

Comparing the circumferences measured with the different tape measures, the measured

girth values differed significantly and were smaller for the Gulick I and Waegener tape

measures than for the Gulick II and standard tape measure (Table 17). This can be

explained by the amount of tension applied to the tape and thereby on the soft tissue. When

handled correctly, a six ounce tension was applied with the Gulick I tape measure, which

was higher than the Gulick II tape measure tension (four ounces). The tension applied with

the Waegener tape measure was unknown, but due to the results, one might speculate that

the tension value was between four and six ounces. Observers were instructed not to apply

tension on the standard tape measure, and results show that they followed these

instructions on the whole. The limit of reproducibility was lowest for the Gulick II tape

measure and highest for the Waegener tape measure, although the differences between the

Gulick I, standard and Waegener tape measures were rather small. This indicates that

reproducibility of circumferential measurements obtained with expensive devices, i.e.


Gulick I and Gulick II tape measures, were not higher than those obtained with

inexpensive devices, i.e. Waegener and standard tape measures.

Tape Mean ± SD t1: O1-O2 t2: O1-O2 O1: t1-t2 O2: t1-t2

SDD

ICC SDD

ICC SDD

ICC SDD

ICC

GI 36.3 ± 3.1 0.5-1.2 0.97-0.98 0.4-1.3 0.97-0.99 0.9-1.3 0.97-0.98 0.9-1.3 0.97-0.98

GII 37.6 ± 3.4 0.6-2.1 0.93-0.98 0.5-1.8 0.94-0.99 1.0-1.7 0.95-0.98 1.0-1.4 0.96-0.97

S 37.5 ± 3.3 0.7-1.7 0.95-0.98 0.7-1.2 0.98-0.99 1.0-1.2 0.97-0.98 0.9-1.1 0.98

W 36.7 ± 2.9 0.6-0.9 0.98 0.6-1.0 0.98-0.99 1.0-1.1 0.97-0.98 0.9-1.2 0.97-0.98

Table 17: Comparison of measuring tapes

t1: O1-O2, inter-observer reproducibility on first measuring day; t2: O1-O2, inter-observer reproducibility on second

measuring day; O1: t1-t2, intra-observer reproducibility of observer O1; O2: t1-t2, intra-observer reproducibility of

observer O2

Studies investigating the reproducibility of different tape measures are hard to find in

literature. Harrelson et al. (1998) performed lower extremity circumference measurements

in twenty-one subjects at three measurement sites with a standard tape measure and a

Lufkin tape measure with a Gulick spring-loaded handle attached, comparable to the

Gulick I tape measure used in this study [67]. They reported high reliability but a

significant difference between the two tape measures and stated that the Lufkin tape

measure with the Gulick handle attachment was associated with less measurement error

and was therefore preferable to a standard tape measure. Geil (2005) investigated the

accuracy and reliability of a standard tape measure, a spring tape measure and a

circumferential tape measure, comparable to the Gulick I and Waegener tape measures,

respectively, used in the present study on three foam positive models of transtibial amputee

residual limbs and concluded that the type of tape measure used did not affect the results

[94]. However, the measurements were performed on foam models with fixed marking of

the measurement sites, limiting the comparability to other studies.

Baker et al. (2010) evaluated four different devices for obtaining circumferential

measurements at four locations on the canine hindlimb and forelimb (the Gulick II tape

measure, a retractable tape, an ergonomic tape measure and a circumference measuring

tape comparable to the Waegener tape measure used in the present study). They stated that

devices were equally precise for repeated measurements although the absolute

measurement varied by device. The measurements with the ergonomic and circumference

measuring tapes were significantly larger than with the retractable and Gulick II tape

measures [92].


4.1.1.4 Influence of experience and profession of observers on reproducibility

In order to assess a possible influence of tester experience and profession on girth

measurements, five observers with different degree of experience in girth measurements

covering a broad spectrum of medical and non-medical professions were selected (Table

3). The observers O4 and O5 had no medical background and had never before assessed

lower leg circumference with any tape measure used in this study. Observer O1 was a

student of both medicine and electrical engineering, while observer O2 was a medical

resident and observer O3 an orthopaedic surgeon. Further, the observers O1, O2, and O3

had experience in the usage of one of the used tape measures (Waegener tape measure) in

girth measurements. There were differences in the degree of experience between the

observers O1, O2, and O3. While the observers O1 and O2 had used the Waegener tape

measure over a couple of months prior to the study, observer O3 had only occasionally

performed circumferential measurements with this tape measure. None of the observers

had clinical experience with the other measuring tapes (Gulick I, Gulick II plus, and

standard tape measures).

A comparison of the observers across measurement sites and tape measures showed that

the observers O1 and O2 had the highest intra-observer agreement (SDD range, 0.7 to 1.5

cm, and 0.5 to 1.4 cm, respectively) (Table 18). The observers O3 and O5 showed lowest

agreement (SDD range, 1.1 to 3.3 cm, and 0.6 to 2.5 cm, respectively), while the observer

O4 ranked in between (SDD range, 0.9 to1.8 cm). This was also reflected by the range of

ICC values, showing higher reliability for the observers O1, O2 and O4 (range, 0.97 to

0.99, 0.97 to 1.00 and 0.97 to 0.99), than for the observers O3 and O5 (range, 0.88 to 0.99

and 0.92 to 1.00, respectively).

Considering the different measuring tapes, observer O1 had very similar SDDs for the

Gulick I, standard and Waegener tape measures (range, 0.7 to 1.0 cm, 0.9 to 1.0 cm, and

0.9 cm, respectively), which was also reflected by the corresponding ICC values (range,

0.98 to 1.00 and 0.99), but lower SDD and ICC values for the Gulick II plus tape measure

(SDD range, 0.8 to 1.5 cm and ICC range, 0.97 to 0.99). Observer O2 showed higher

reproducibility for the Waegener and standard tape measures (SDD range, 0.7 to 1.1 cm

and 0.5 to 1.3 cm, and ICC range, 0.98 to 0.99 and 0.98 to 1.00, respectively), than for the

Gulick II and Gulick I tape measures (SDD range, 0.7 to 1.4 cm and 0.8 to 1.4, and ICC

range, 0.97 to 0.99 and 0.98 to 0.99). For observer O3, agreement and reliability were

highest for the Gulick I tape measure (SDD range, 1.1 to 1.2 cm and ICC 0.98) and lowest

for the Gulick II plus tape measure (SDD range, 1.3 to 3.3 cm and ICC range, 0.88 to


0.99). For observers O4 and O5, reproducibility was lowest for the Gulick II plus tape

(SDD range, 1.1 to 1.8 cm and 1.2 to 2.5 cm, and ICC range, 0.97 to 0.99 and 0.92 to 0.98,

respectively). While observer O4 reached highest reproducibility with the Waegener tape

measure (SDD range, 0.9 to 1.1 cm and ICC range, 0.98 to 0.99), observer O5 performed

similar with the Gulick I, standard tape and Waegener measures (SDD range, 1.1 to 1.9

cm, 0.6 to 2.0 cm and 0.7 to 2.0 cm, and ICC range, 0.95 to 0.98, 0.95 to 1.00, and 0.95 to

0.99, respectively).

Site Tape O1 O2 O3 O4 O5

SDD ICC SDD ICC SDD ICC SDD ICC SDD ICC

PP GI 1.0 0.99 1.4 0.98 1.2 0.98 1.5 0.98 1.9 0.96

GII 1.5 0.97 1.4 0.97 3.3 0.88 1.8 0.97 2.5 0.92

S 1.0 0.99 1.3 0.98 1.8 0.96 1.6 0.98 1.6 0.97

W 0.9 0.99 1.0 0.99 1.7 0.96 1.1 0.99 2.0 0.95

MP GI 0.7 0.99 0.8 0.99 1.1 0.98 1.1 0.98 1.1 0.98

GII 0.8 0.99 0.7 0.99 1.6 0.96 1.2 0.98 1.2 0.98

S 0.9 0.99 0.6 0.99 1.3 0.97 1.3 0.98 0.6 1.00

W 0.9 0.99 0.7 0.99 1.5 0.96 1.0 0.98 0.7 0.99

DP GI 1.0 0.98 0.8 0.99 1.2 0.98 0.9 0.99 1.7 0.95

GII 1.1 0.98 0.8 0.98 1.3 0.99 1.1 0.98 2.0 0.94

S 0.9 0.99 0.5 1.00 1.5 0.97 1.1 0.98 2.0 0.95

W 0.9 0.99 1.1 0.98 1.1 0.98 0.9 0.99 1.8 0.95

Table 18: Girth - Intra-observer reproducibility for the observers O1-O5 (n= 10 legs)

A comparison of the percentage of intra-observer differences exceeding 1.0 cm, 1.5 cm,

and 2.0 cm shows that the difference between measuring days measured by the observers

O1 and O2 never exceeded 1.5 cm, in contrary to the other observers (Table 19). For

observer O1, the difference between measuring days exceeded 1 cm in only two cases (at 7

cm proximal of mid-patella measured with the Gulick II plus tape measure, and at mid-

patella, measured with the standard tape measure).

In summary, the results of the girth measurements by the observers O1, O2, O3, O4 and

O5 showed remarkable variations. As was to be expected, the most experienced observers

O1 and O2 performed best. However, observer O3 with occasional experience in girth

measurements showed lower performance than the inexperienced observer O4. One could

speculate that reproducibility can only be increased if the observer regularly performs girth


measurements. Another explanation for these findings may be that it is not experience, but

talent, which has a greater influence on repeatability in girth measurements.

Site Tape D >1.0 cm [%] D >1.5 cm [%] D >2.0 cm [%]

O1 O2 O3 O4 O5 O1 O2 O3 O4 O5 O1 O2 O3 O4 O5

PP GI 0 20 0 10 30 0 0 0 0 10 0 0 0 0 0

GII 10 20 50 10 40 0 0 20 10 30 0 0 20 10 0

S 0 0 30 20 10 0 0 0 0 10 0 0 0 0 0

W 0 0 20 10 30 0 0 0 0 10 0 0 0 0 0

MP GI 0 0 0 0 10 0 0 0 0 0 0 0 0 0 0

GII 0 0 20 10 10 0 0 0 10 0 0 0 0 0 0

S 10 0 10 10 0 0 0 0 0 0 0 0 0 0 0

W 0 0 20 0 0 0 0 0 0 0 0 0 0 0 0

DP GI 0 0 10 0 20 0 0 0 0 10 0 0 0 0 0

GII 0 0 0 0 20 0 0 0 0 10 0 0 0 0 0

S 0 0 10 10 30 0 0 0 0 10 0 0 0 0 0

W 0 10 0 0 20 0 0 0 0 10 0 0 0 0 0

Table 19: Percentage of differences exceeding 1 cm, 1.5 cm, and 2 cm (O1-O5)

Harrelson et al. (1998) stated that reliability of lower extremity circumference

measurements was not influenced by tester experience [67]. In their study, an athletic

trainer and a graduate assistant athletic trainer measured lower extremity girth at three sites

in twenty-one subjects using a standard flexible tape measure and a Lufkin tape measure

with a Gulick spring-loaded handle attachment, comparable with the Gulick I tape measure

used in this study. However, no information could be found in their publication

considering the experience of the testers in girth measurements. Further, Jakobsen et al.

(2010) reported that tester experience appeared not to influence the degree of reliability

[4]. In their study, an experienced physiotherapist with 10 years of experience in

orthopaedic physiotherapy and an inexperienced physiotherapy student performed

circumference measurements in nineteen outpatients having received a TKA, using a non-

elastic tape measure at 1 cm proximal of the base of the patella.

In general, the previously reported studies considering tester experience compared only

one experienced observer with one inexperienced observer. In order to make a statement

about the influence of tester experience on reproducibility of a measuring device,


measurements taken by a larger number of experienced and inexperienced testers should be

compared.

The corresponding Bland and Altman plots for the measurement sites 7 cm proximal of

mid-patella, mid-patella, and 7 cm distal of mid-patella are to be found in Figure 45, Figure

46, Figure 47, Figure 48 and Figure 49, respectively, in the appendix. Further, there are

detailed tables of the results of the inter-observer and intra-observer analysis for the

observers O1-O5, including mean difference with confidence intervals, standard deviation

of the mean difference, limits of agreement with confidence intervals, and the ICCs with

confidence intervals in the appendix (A.2.1.1 and A.2.1.2, respectively).

4.1.2 Sources of measurement error

In general, measurement error can originate from the measurement device itself, i.e., tape

measure used, the user, and the subject [80]. In particular, sources of measurement error of

girth measurements in this study include the determination of the measurement sites, the

alignment of the measuring tape perpendicular to the leg axis, the use of the tape measures

as recommended in the user´s manual, the applied tension on the tape, and reading errors.

Further, biological changes might have an influence on the subject´s lower extremity

circumference. Apart from that, a learning effect might be present which may cause higher

variation mimicking less reproducibility. Additionally, the examined lower extremities of

the subjects were considered independent entities because it was assumed that there was no

influence of leg side on the assessment of reproducibility. Finally, the sample size was

limited.

4.1.2.1 Determination of the measurement sites

The measurement sites for this study were defined at 7 cm proximal of mid-patella, at mid-

patella, and at 7 cm distal of mid-patella because of two reasons. First, it was thought that

these measurement sites are appropriate to describe circumferential changes due to

swelling after TKA. Second, it was assumed that the upper and lower boarder of the patella

were simply identifiable bony landmarks.

To determine the measuring positions, the first step was to identify the upper and lower

patella borders in order to determine the mid-patella. During measurements, it turned out

that this was a difficult task in some subjects due to a varying proportion of surrounding

soft tissue in the knee region.

If an observer failed to identify the patella borders correctly, the marks for the different

measurement sites subsequently differed from other observers and maybe even from one


measuring point of time to the other of the same observer. As a consequence, the girth was

measured at a different site, which, in turn, led to different the measured circumferences,

increasing the inter-observer and intra-observer variation. To investigate this possible

source of error, the observers were asked to document the measured length of patella,

which was used to identify the mid-patella site by division by 2. Table 20 shows the mean

longitudinal length of the left and right patella on the first and second measuring day and

the differences in measured patella length between measuring days. The patella length

ranged from 4.0 to 7.0 cm. In literature, the mean longitudinal length ± SD of the patella

has been reported to range from 40 ± 2.6 mm for females to 45.6 ± 3.0 for males in MRI

measurements [95] and 3.70 ± 0.29 cm for females to 4.12 ± 0.29 cm for males in

skeletons [96]. The values in this study are higher (females 5.1 cm, range 4.0 to 6.1 cm and

males 5.6 cm, range 4.6 to 7.0 cm), because patella length was estimated by palpation on

the body surface and thus the soft tissue inevitably enlarged the measured length.

The difference in patella length between measuring days ranged from 0.0 to 1.5 cm, which

was up to 37.5% for a patella of 4 cm in length. Interestingly the inter-observer variation

was smallest for the observers O3 and O5, who had shown the least reliability and

agreement in girth measurements. This may indicate that other sources of variation make a

greater contribution to the total measurement error.

Observer Mean length t1 (cm) Mean length t2 (cm) Mean difference t1-t2 (cm)

Left patella Right patella Left patella Right patella Left patella Right patella

O1 5.6 (5.1-6.4) 5.3 (4.0-6.0) 5.4 (4.6-6.5) 5.4 (4.3-6.5) 0.4 (0.0-0.4) 0.6 (0.0-1.5)

O2 5.2 (4.6-6.2) 5.1 (4.5-6.0) 5.2 4.0-6.5) 5.2 (4.0-6.6) 0.7 (0.2-1.3) 0.7 (0.2-1.5)

O3 5.5 (4.8-6.1) 5.5 (4.8-6.2) 5.4 (5.0-6.0) 5.4 (5.0-6.0) 0.2 (0.0-0.5) 0.2 (0.0-0.5)

O4 5.5 (5.0-6.2) 5.6 (5.0-7.0) 5.8 (4.6-6.5) 5.8 (4.5-7.0) 0.6 (0.0-1.0) 0.7 (0.0-1.5)

O5 5.3 (4.8-6.0) 5.3 (4.7-6.0) 5.2 (4.9-6.1) 5.2 (4.7-6.2) 0.3 (0.0-1.0) 0.4 (0.0-1.0)

Table 20: Mean difference in measured patella length for the observers O1-O5

With range of length in semicolons; t1, first measuring day; t2, second measuring day

4.1.2.2 Alignment and use of the tape measures

Prior to the first measurement day, the use of the tape measures as recommended in the

user´s manual was shown to the observers. In case of the standard tape measure, the

observers were instructed to avoid applying tension to the tape.


Apart from that observers were instructed to measure circumferentially, not elliptically.

However, there was no training of the observers prior to the measurements. One could

speculate that reproducibility was higher if the observers had pre-study training in the

correct use of the tape measures.

The lower reproducibility of girth measurements at the measurement site 7 cm proximal of

mid-patella might be explained by the cylindrical shape of the thigh and less firm soft

tissue in this region, in combination with elliptically misalignment of the tape measure.

4.1.2.3 Biological changes

Lower extremity circumference may change from day to day, and during the day, due to

time of day, outside temperature, and physical load between measurements. The

measurements were performed at different daytimes and outdoor temperatures.

Further, there was a gap of five days between the measuring days. Although the subjects

were asked to avoid excessive physical loading prior to and between the measurement

days, it cannot be ruled out that there was a change in lower extremity girth due to

biological changes.

Te Slaa at al. reported that reliability of repeated tape measurements decreased when the

time interval between measurements increased and explained this drop in reliability by

biological fluctuations [39].

4.1.2.4 Reading errors

Reasons for reading the wrong numbers from the tape measure might be an ambiguously

defined zero line, an inadequate font size of the scaling, or a disadvantageous scaling. Of

the measurement tapes used in this study, only the Gulick tape measure had a clear zero

line. In case of the Gulick II plus and standard tape measure, the end of the tape was the

zero line. The zero line of the Waegener tape measure was determined by the entry

opening of the tape into the housing. Depending on the viewing angle, the zero line thus

changed because it was not part of the tape, but of the housing.

The orientation of the numbers printed on the scaling in direction of the tape axis on the

Gulick I and Gulick II plus tape measures, and perpendicular to the axis of the tape on the

Waegener and standard tape measures (Figure 33, from top in this order).

The scale of the Gulick I tape measure turned out to be disadvantageous. Only the tens on

the tape consisted of first and second digit, while the numbers in between consisted of one

digit instead of two, e.g., 10-1-2-3-4-5-6-7-8-9-20 (Figure 33, tape on the top). This made

the reading more difficult and prone to error. Further, the observer had to ensure that the


side with the metric scale faced upwards to report measurements in cm. In case of the

Gulick II plus tape measure, both a metric and an inch scale were found on one side of the

tape, and only an inch scale on the other tape side. Thus the observer had to ensure to read

from the right scale (cm).

Figure 33: Scales of the used tape measure

4.1.2.5 Learning effect

Eighty percent of the observers stated in the questionnaire that their measurement

reliability and agreement would improve with the duration of the measurement procedure

because they got used to handling the measuring tapes. Thus, to consider a possible

learning effect, the results of inter-observer reproducibility of the first and second

measuring day are compared in Table 21. These day to day comparisons were made for the

observers O1 and O2 only, who measured all subjects, because a learning effect was

considered unlikely for those observers who measured only five subjects.

Inter-observer reproducibility was substantially higher for the second measuring day than

for the first (SDD range, 0.7 to 1.8, and 0.7 to 2.1 cm, respectively, and ICC range, 0.94 to

0.99 and 0.93 to 0.98, respectively). In particular, agreement improved for all measurement

sites, with 7 cm proximal of mid-patella and at mid-patella showing higher differences in

maximum SDD (-0.3 cm) than 7 cm distal of mid-patella (-0.1 cm). Considering the

different tape measures, agreement improved for the Gulick II and standard tape measures

(-0.3 cm and -0.5 cm, respectively).

Summarising these results, improvement in reproducibility between first and second

measuring day was observed for all measurement sites as well as the Gulick II and the

standard tape measures. It is likely that the observers improved in tape positioning and

usage of the tape measures.


Site Tape t1: O1-O2 t2: O1-O2

mD ± SDdiff LOA SDD ICC mD ± SDdiff LOA SDD ICC

PP GI 0.2 ± 0.5 -0.9 to 1.2 1.2 0.97 0.2 ± 0.6 -1.0 to 1.3 1.3 0.97

GII 0.4 ± 0.8 -1.2 to 2.1 2.1 0.93 0.2 ± 0.8 -1.4 to 1.8 1.8 0.94

S 0.3 ± 0.7 -1.0 to 1.7 1.7 0.95 0.1 ± 0.6 -0.9 to 1.2 1.2 0.98

W 0.0 ± 0.4 -0.8 to 0.9 0.9 0.98 0.1 ± 0.5 -0.8 to 1.0 1.0 0.98

MP GI 0.0 ± 0.5 -0.9 to 1.0 1.0 0.97 0.0 ± 0.4 -0.8 to 0.8 0.8 0.98

GII -0.1 ± 0.6 -1.2 to 1.0 1.2 0.97 -0.1 ± 0.3 -0.8 to 0.5 0.8 0.99

S 0.2 ± 0.5 -0.7 to 1.1 1.1 0.97 0.2 ± 0.4 -0.5 to 0.9 0.9 0.98

W 0.0 ± 0.4 -0.8 to 0.9 0.9 0.98 0.1 ± 0.3 -0.5 to 0.7 0.7 0.99

DP GI -0.2 ± 0.4 -0.9 to 0.5 0.9 0.98 -0.1 ± 0.3 -0.7 to 0.4 0.7 0.99

GII -0.2 ± 0.4 -1.0 to 0.6 1.0 0.98 -0.1 ± 0.4 -0.9 to 0.7 0.9 0.98

S 0.0 ± 0.4 -0.7 to 0.7 0.7 0.98 0.1 ± 0.3 -0.5 to 0.7 0.7 0.99

W -0.2 ± 0.4 -1.0 to 0.6 1.0 0.98 -0.2 ± 0.4 -0.9 to 0.6 0.9 0.98

Table 21: Girth - Inter-observer reproducibility of first and second measuring day

4.1.2.6 Left vs. right leg

In clinical routine, a measuring tape has to show high reproducibility in assessing the

circumference of the involved leg. Thus, differences between left and right leg were not

considered clinically relevant and, therefore, both legs were treated as independent entities

for statistical analysis. Further, it was hypothesised that differences in reproducibility of

girth measurements between left and right leg do not exist. To test this assumption, the

SDD and ICC values of the left and right lower extremity were compared. It was found

that agreement (SDD) of left and right leg differed considerably, in inter-observer

comparison for the first (SDD range, 0.7 to 1.4 cm and 0.9 to 2.5 cm, respectively) and

second measuring day (SDD range, 0.6 to 1.4 and 0.6 to 2.2 cm, respectively), and in intra-

observer comparison for observer O1 (SDD range, 0.8 to 1.4 cm and 1.1 to 2.0 cm,

respectively). Observer O2 showed no side differences in SDD (range, 0.7 to 1.6 cm).

Having a closer look at the results of observer O1 in Table 22, it shows that reproducibility

was higher for the left leg (SDD range, 0.8 to 1.4 cm and ICC range, 0.96 to 0.99) than for

the right leg (SDD range, 1.1 to 2.0 cm and ICC range, 0.94 to 0.98). Further, the

measurement site at 7 cm proximal of mid-patella and the Gulick II plus and standard tape

measures showed highest leg differences. Differences in SDD between left and right leg


were negligible at the measurement site 7 cm distal of mid-patella and for the Waegener

tape measure.

These results indicate that handedness of the observers may have an influence on

reproducibility of circumferential leg measurements.

O1 O2

Left leg Right leg Left leg Right leg

SDD ICC SDD ICC SDD ICC SDD ICC

total 0.8 to 1.4 0.96 to 0.99 1.1 to 2.0 0.94 to 0.98 0.7 to 1.6 0.95 to 0.99 0.7 to 1.6 0.95 to 0.99

PP 0.9 to 1.4 0.96 to 0.99 1.1 to 2.0 0.94 to 0.98 1.2 to 1.6 0.95 to 0.98 1.2 to 1.6 0.96 to 0.98

MP 0.8 to 1.0 0.97 to 0.99 1.1 to 1.3 0.96 to 0.98 1.0 to 1.1 0.97 to 0.98 0.7 to 1.2 0.97 to 0.99

DP 0.9 to 1.3 0.96 to 0.98 1.1 to 1.3 0.97 to 0.98 0.7 to 1.1 0.98 to 0.99 1.0 to 1.5 0.95 to 0.98

GI 0.8 to 1.2 0.98 to 0.99 1.1 to 1.3 0.96 to 0.98 0.9 to 1.5 0.97 to 0.99 0.7 to 1.4 0.97 to 0.99

GII 0.8 to 1.4 0.96 to 0.98 1.1 to 2.0 0.94 to 0.98 1.0 to 1.6 0.95 to 0.98 1.2 to 1.6 0.95 to 0.97

S 1.0 to 0.9 0.98 to 0.99 1.1 to 1.4 0.96 to 0.97 1.0 to 1.2 0.98 to 0.98 0.9 to 1.4 0.98 to 0.98

W 1.0 to 1.1 0.97 to 0.98 1.1 to 1.1 0.97 to 0.98 0.7 to 1.3 0.98 to 0.99 0.9 to 1.4 0.96 to 0.98

Table 22: Left and right leg intra-observer comparisons (SDD and ICC) (n=18)

4.1.2.7 Number of cases

The sample size for this study was limited. 20 subjects voluntarily participated in the study.

On the first measuring day, all 40 legs of the 20 subjects were measured by observers O1

and O2. Two of the 20 subjects did not return for measurements on measuring day two

(10%). Observers O3, O4, and O5 measured only 10 legs of five subjects (25%). The small

sample size may reduce the statistical power of the results. It should be noted that all of our

subjects were healthy individuals and, thus, the generalizability of our results to a patient

population may be limited. This applies equally to the goniometric measurements.

4.1.3 Usability of the different tape measures

Although reliability and agreement are essential features, the usability of a measuring

device used in the clinical setting plays a non-negligible role. To assess the user-

friendliness of the four different measuring tapes used in this study, the observers were

asked to fill in a questionnaire after the first measuring day (Questionnaire on the usability

of the measuring tapes). This questionnaire contained questions on the pre-study clinical

experience of the observers with the used tape measures, the advantages and disadvantages


of each tape measure, the precision of each measuring tape and the required measurement

time.

Three of the five observers (60% - O1, O2, and O3), had experience in handling one of the

used tape measures (Waegener tape measure). While the observers O1 and O2 had used the

Waegener tape measure over a couple of months prior to the study, observer O3 had only

occasional experience. None of the observers had clinical experience with the other

measuring tapes (Gulick I, Gulick II plus, and standard tape measures).

In the questionnaire, the observers were asked to rank each tape measure according to its

level of usability. All five observers ranked the Waegener tape measure the most user

friendly tape measure. Four of five observers (83%) ranked the Gulick II plus tape measure

the least user friendly tape measure, while one observer selected the standard tape measure

as the least easy-to-use measuring tape.

Another question addressed the subjective feeling of the observers concerning the

precision of the tape measures. Four of five observers ranked the Waegener tape measure

the most precise tape measure, while one observer selected the standard tape measure as

the most precise measuring tape. However, the observers were less agreed on the least

precise tape measure. Three observers selected the Gulick II plus tape measure, one

observer the standard tape measure, and another observer the Gulick I tape measure to be

the least precise one. When asked for the required measuring time, there was consensus

that the Waegener tape measure enabled the quickest measurement. Four of five observers

(80%) stated that the measurement took longest with the GII tape measure, while one

observer selected the Gulick II plus tape measure to be the most time consuming.

Interestingly, none of the observers felt that the accuracy of measurements decreased with

the duration of the measurement procedure due to increasing fatigue. On the other hand,

four of five observers thought that their measuring accuracy increased with the duration of

the measurement procedure because they got used to handling the measuring tapes.

When asked about the most important features of the Waegener tape measure which was

considered the most user-friendly, all observers answered that easy handling and quick

measuring due to the suspension mechanism were reasons to choose this tape measure. In

this context, an easy to read scaling, a clearly visible zero line, an easy alignment of the

tape, and a tape that doesn’t slip were important properties (80%). Further, four of five

observers stated that a precise measurement was a reason for choosing the Waegener tape

measure.


Conversely, reasons for choosing the Gulick II plus tape measure as the least user-friendly

were complicated handling (100%), long measuring time (100%), and difficult alignment

due to tape thickness (80%). Four of five observers criticised that the tape easily slipped

because it was too thick and therefore the contact surface between skin and tape too small,

due to the conical leg shape.

Considering the tension control provided by the Gulick I, Gulick II plus, and Waegener

tape measures, the tension applied by the Gulick I tape measure was considered too tight,

while the tension of the Gulick II plus was considered too weak to tighten the tape. In

general, the observers appreciated the tension control insofar as it increases the precision of

the measurement. However, in case of the Gulick I and Gulick II plus tape measures,

correct application of the tensioning device made them more difficult to handle. This was

partly due to the fact that both hands were necessary for the measurement - one hand for

the tensioning device and the other hand for stabilising the tape. If the observer had to

reposition the tape, e.g. because it was not aligned perpendicular to the longitudinal axis of

the leg, it was not possible to do the correction without releasing the tape and starting the

measuring procedure from the beginning. As a consequence, the measurements with the

Gulick I and Gulick II plus tape measures took longer compared with the standard and

Waegener tape measures. Furthermore, the marking for the correctly applied tension was

hard to identify in case of the Gulick I tape measure (Figure 11, left picture). Another

reported disadvantage of the Gulick I and Gulick II plus tape measures was the scale on the

tapes (see chapter 4.1.2.4).

While the numbers of the scaling on the Gulick I tape measure were of adequate type size,

this did not apply for the Gulick II plus tape measure. One side of the tape provided a scale

in inches, and the other side one scale in inches and one in cm. Thus, the font size of the

metric scale was very small.

Although the Waegener tape measure showed the highest usability, one big disadvantage

was the short life cycle of this product. The tape was torn at the pin after a few

measurements. Further, the amount of tension applied to the tape was unknown and was

felt to decrease with time.

In this study, reproducibility strongly depended on the tape measure used. The Waegener

tape measure showed highest reliability for four of five observers. This tape measure was

also selected the most user-friendly tape measure by all five observers. Further, four of five

observers stated that they had the feeling to perform most precise with the Waegener tape

measure, which was true for four of five observers. These results show that the most user-

Discussion - Discussion of the flexion reproducibility measurements 71

friendly tape measure also provided the most reproducible results. Thus it is recommended

that the tape measure preferred by the clinician should be used for lower extremity girth

measurements, if possible.

4.2 Discussion of the flexion reproducibility measurements

4.2.1 Discussion of the results

Based on the results of inter-and intra-observer agreement, the smallest detectable

differences for goniometric measurements would lie between 5.9 and 9.0°, thus within the

a priori criterion of 10°. Inter-observer reproducibility was slightly higher for the second

measuring day. Further, observer O1 showed slightly higher agreement than observer O2

in intra-observer comparisons. Reliability was acceptable to high, with ICC values ranging

from 0.85 to 0.99.

Intra-observer and inter-observer reproducibility were comparable. This is in contradiction

to most previous reports on goniometric measurements of the knee joint reporting higher

intra-tester reliability and/or agreement [4,45,48,74,75,77].

Measurements SDD (°) ICC

total 5.9 to 9.0 0.87 to 0.99

t1: O1-O2 5.9 to 8.2 0.88 to 0.99

t2: O1-O2 7.6 to 9.0 0.85 to 0.98

O1: t1-t2 7.1 to 7.7 0.90 to 0.98

O2: t1-t2 7.1 to 8.1 0.87 to 0.98

Table 23: Flexion: Summary of the results (observers O1 and O2)

t1: O1-O2, inter-observer reproducibility on first measuring day; t2: O1-O2, inter-observer reproducibility on second

measuring day; O1: t1-t2, intra-observer reproducibility of observer O1; O2: t1-t2, intra-observer reproducibility of

observer O2

Several published studies have addressed the reliability of goniometric measurements

[47,48,74,75,78,81], but only a few reliability and agreement [4,5] (Table 24). The findings

of our study agree with those of previous investigators who also demonstrated acceptable

to high intra-tester reliability [4,48,74-77,79,82]. Compared with previous reports, the

inter-tester reliability in this study was within the range of observed values or slightly

higher.

Generally, higher reliability was reported for knee flexion than for extension. Rothstein et

al (1983) found high intra-tester reliability for knee flexion and extension (ICC, 0.97-0.99).


Inter-tester reliability was high for knee flexion (0.89 to 0.92), but poor for knee extension

(ICC 0.61 to 0.70). This is in agreement with Clapper (1988) et al., who observed high

intra-observer reliability for knee flexion (ICC, 0.95) and acceptable intra-observer

reliability for extension (ICC, 0.85). Watkins and colleague (1991) reported higher intra-

tester and inter-tester reliability for knee flexion (ICC 0.99 and 0.90) than for knee

extension (0.98 and 0.86) [48]. Käfer et al (2005) examined the reliability of visual

estimation and goniometric measurements of knee range of motion. Intra-observer and

inter-observer agreement was consistent regarding the goniometric assessment of flexion

(rs>0.6), whereas reliability was uniformly low for both measurements regarding the

assessment of extension (rs<0.6) [78].

Brosseau et al. (2001) reported very high intra-tester reliability in flexion (ICC, 0.997) and

in extension (ICC, 0.972 to 0.985) for measurements with a universal goniometer. The

inter-tester reliability was also high for flexion (ICC 0.977 to 0.982) and for extension

(ICC 0.893 to 0.926) [75].

While most studies evaluated only reliability of goniometric measurements, only two

addressed agreement of universal goniometers [4,5]. Lenssen et al. (2007) assessed inter-

observer reproducibility of active and passive measurements of knee ROM using a long

arm goniometer in TKA patients within the first four days after surgery. For passive

flexion with the patient in supine position, they reported a mean difference of 1.4° with

limits of agreement from 16.2° to 19.0° for the difference between the two observers. The

corresponding ICC value was 0.88 [5]. In the study of Jakobsen et al. (2010), two

physiotherapists with different clinical experience performed passive knee joint ROM

measurements with a universal goniometer in patients having received a TKA [4]. They

observed high ICC values for intra-observer and inter-observer comparisons (ICC2,1 0.97 to

0.98, smallest real difference SRD 5.1-6.2° and ICC2,1 0.96, SRD 6.4 to7.1°, respectively).

Joint mobility can be determined by visual estimation, universal goniometers, or

measurement of joint angles after X-ray visualisation in maximum flexion or extension

[45]. Opinions vary on the method that should be used to measure knee ROM. Watkins and

colleagues examined intra-observer and inter-observer reliability of therapists who

performed hand goniometry and visual estimation, and concluded that hand goniometry

was superior to visual estimation for consistency of measurement [48]. This is in

agreement with Lavernia et al. (2008) who stated that assessment of ROM through direct

observation without a goniometer provides inaccurate findings [35]. Käfer et al (2005)

reported comparable reliability for visual and goniometric assessment of knee range of


motion [78]. Conversely, Peters et al. found higher intra-observer and inter-observer

reliability for visual estimation than for hand goniometry [79]. Watkins and colleagues

(1991) examined the intra-observer and inter-observer reliability of hand goniometry and

visual estimation of knee range of motion. They found interobserver reliability for hand

goniometry to be 0.90 for flexion and 0.86 for extension, compared with 0.83 and 0.82 for

flexion and extension, respectively, for visual estimation [48].

Study Goniometer type Intra-observer reliability/ Inter-observer reliability/

agreement agreement

Rothstein et al. (1983) Plastic goniometer, L=15.24 cm

Plastic goniometer, L=25.4 cm

Metal goniometer, L=30.5 cm

ICC: 0.99

ICC: 0.99

ICC: 0.97

ICC: 0.61-0.70

ICC: 0.61-0.63

ICC: 0.59-0.80

Gogia et al. (1987) Standard plastic goniometer,

L=30 cm

ICC: 0.99

Clapper et al. (1988) Standard goniometer ICC: 0.95

Rheault et al. (1988)

Plastic universal goniometer,

L=25.4 cm

Pearson´s r: 0.87

Watkins et al. (1991)

Plastic universal goniometer,

L=12.7 cm

ICC: 0.99 ICC: 0.90

Brosseau et al. (1997)

Universal goniometer ICC: 0.86-0.94a

ICC: 0.95-0.97b

ICC: 0.62-0.70a

ICC: 0.91-1.00b

Brosseau et al. (2001)

Universal plastic goniometer,

L= 25 cm

ICC: 0.997 ICC: 0.977-0.982

Edwards et al. (2004)

Standard goniometer,

L=30.5 cm

Correlation coefficient

(no type specified): 0.92

Correlation coefficient

(no type specified): 0.79

Käfer et al. (2005) Universal goniometer Spearman rS: 0.65-0.76 rS: 0.62-0.69

Lenssen et al. (2007)

Long-arm goniometer ICC: 0.88c, SDD: 17.6°

LOA: -16.2-19.0°

Jakobsen et al. (2010)

Plastic goniometer,

L=30 cm

ICC2,1: 0.97-0.98

SRD: 5.1-6.2°

ICC2,1: 0.96

SRD: 6.4-7.1°

Peters et al. (2011) Standard plastic goniometer,

L=18 cm

ICC: 0.96-0.98d ICC: 0.70-0.95d

Table 24: Knee flexion in literature

L, length of goniometer arm; a small angles, b large angles, c passive flexion supine, d mean of two observers; length of

goniometer arms reported in inches were converted to cm;


However, one has to be careful in comparing the results of different studies because of

different study designs, different subjects evaluated (healthy subjects vs. patients), and

different methods for statistical analysis. For example, Brosseau et al. (2001) reported very

high reliability for goniometric measurements [75]. This might be explained by their

measurement procedure, in which one independent observer had placed markers over the

bony landmarks and the same markers were used by all testers. This approach seems

questionable because an important source of error - the identification of the bony landmark

by the observers – was eliminated. Thus, the reported ICC values did not reflect total

reliability of the method. Rothstein et al. (1983), Watkins (1991), and Jakobsen (2009)

used goniometers with covered scales [4,48,82]. The observer aligned the arms of the

blinded goniometer and gave the goniometer to a data recorder who uncovered the scale

and recorded the measurement obtained. This procedure was justified by the authors to

avoid influence of the observers by the results of the measurement. Nevertheless, the

reported reliability did not account for reading errors by the observer.

Considering statistical analysis, most of the cited studies used intraclass correlation

coefficient as a measure for reliability. In this study, the ICC2,1 as described by Shrout and

Fleiss was used to describe the degree of reliability of the measurements. This type of ICC

was used by some of the cited studies [4,47,75,76]. However, the type of ICC was not or

not sufficiently specified in other cases [5,79,82], or different to the ICC2,1 [48,75]. This

makes comparisons difficult since the resulting ICC value varies depending on which

version of the ICC is used [56,57]. Further, Rankin and Stokes (1998) pointed out that

“regardless of which reliability tests are selected, it appears that comparison of reliability

results between studies is not possible unless the size and attributes of the sample tested in

each case are virtually identical” [63].

4.2.1.1 A priori criterion

Prior to the study, the maximum clinically acceptable SDD was set at 10° for goniometric

measurements, because it was felt that a change in flexion of 10° would be clinically

relevant and should thus be detectable. This criterion was fulfilled in all flexion

measurements (SDD range, 5.9 to 9.0°).

4.2.1.2 Test positions

Reliability of goniometric measurements was reported to depend on the knee angle.

Brosseau et al (1997) have shown higher reliability measurements for larger but not

smaller knee angles [74].Considering the results of this study, agreement for observers O1


and O2 measuring 20 subjects was higher for test position P1 (range, 5.9 to 8.1°) than for

P2 (range, 7.1 to 9.0°). Reliability differed substantially between knee positions P1 and P2,

with ICCs ranging from 0.98 to 0.99 for P1 and from 0.85 to 0.90 for P2. However, for

observers O1-O5 measuring five subjects, intra-observer agreement was comparable

between position P1 (range, 4.9 to 9.1°) and P2 (range, 5.2 to 9.2°). Intra-observer

reliability for observers O1-O5 ranged from 0.40 to 0.91 for position P1 and 0.92 to 0.97

for position P2. These inconsistent results do not allow drawing any conclusions about

reproducibility of test positions.

4.2.1.3 Influence of experience and profession of observers on reproducibility

In order to assess a possible influence of tester experience and profession on

reproducibility of goniometric measurements, five observers with different degrees of

experience in girth and ROM measurements covering a broad spectrum of medical and

non-medical professions were selected (Table 3). The observers O4 and O5 had no medical

background and had never before assessed knee flexion with a universal goniometer, while

the observers O1 and O2 had practised goniometric measurements daily for half of a year

prior to the study. Observer O3 was an orthopaedic surgeon with three years of experience.

The results of the intra-observer reproducibility for the observers O1, O2, O3, O4 and O5

and five subjects are summarized in Table 25. For the interested reader, the corresponding

Bland and Altman plots are to be found in Figure 55 in the appendix (A.2.2.2).

The SDD ranged from 4.9 to 9.2°, and the ICC ranged from 0.40 to 0.97. There was no

significant difference in agreement between the two testing positions P1 and P2 (SDD

range, 4.9 to 9.1 ° and 5.2 to 9.2 °, respectively). However, the corresponding ICC values

were lower for position P1 than for position P2 (range, 0.40 to 0.91, and 0.92 to 0.97,

respectively).

Considering differences between the different observers, observer O4 showed the highest

agreement (SDD range, 6.7 to 7.8°), followed by the observers O1 and O2 (SDD range, 6.9

to 8.2° and 7.2 to 8.3°, respectively). The observers O3 and O5 had lowest SDD values

(range, 4.9 to 9.2° and 5.2 to 9.1°). However, the corresponding ICC values paint a

completely different picture: Observer O3 showed highest reliability (ICC range, 0.91 to

0.92), followed by the observers O1 and O4 (range 0.80 to 0.93 and 0.76 to 0.97) and

observer O5 (range, 0.69 to 0.97). Observer O2 had surprisingly low ICC coefficients

(range 0.40 to 0.92). A closer look at Table 25 reveals that the SDD and ICC values do not

correspond with respect to the level of repeatability. Observer O3, for example, had low

agreement for testing position P2 (SDD, 9.2°), but reliability was high (ICC, 0.94). The


results of observers O1 and O2 measuring all subjects (3.2.3) showed similar contradictory

findings, which will be discussed in chapter 4.3.

In summary, difference in agreement between observers was comparable. This is in

agreement with Käfer et al (2005) and Jakobsen et al. (2010), who reported that tester

experience had no influence on reliability and/or agreement [4,78].

Observer P1: t1-t2 P2: t1-t2

mD ± SDdiff SDD (°) ICC [95% CI] mD ± SDdiff SDD (°) ICC [95% CI]

O1 -2.9 ± 2.1 6.9 0.80 [0.00 , 0.96] -3.9 ± 2.2 8.2 0.93 [0.06 to 0.99]

O2 -3.8 ± 2.3 8.3 0.40 [-0.11 , 0.81] -0.9 ± 3.2 7.2 0.92 [0.73 to 0.98]

O3 -0.7 ± 2.2 4.9 0.91 [0.70 , 0.98] -0.9 ± 4.2 9.2 0.94 [0.79 to 0.98]

O4 -1.6 ± 3.2 7.8 0.76 [0.31 , 0.93] -1.5 ± 2.7 6.7 0.97 [0.87 to 0.99]

O5 -3.2 ± 3.0 9.1 0.69 [-0.01 , 0.92] -1.1 ± 2.1 5.2 0.97 [0.90 to 1.00]

Table 25: Flexion - Intra-observer repeatability (observers O1-O5)

4.2.2 Sources of measurement error

The level of reproducibility of ROM measurements may be influenced by many factors

such as the instruments and procedures applied, the joint examined, or the type of

movement tested [62]. Some investigators have suggested that small joint angles might be

more difficult to measure than large ones [74]. Others have reported that the professional

background had an influence on reproducibility [35]. Further, reproducibility for knee

goniometry relies largely on consistency in the identification of the bony landmarks on the

proximal femur (greater trochanter) and the distal tibia (lateral malleolus) and visualizing

the sagittal axis of movement for the knee joint [44].

Limitations of this study include a possible learning effect, possible differences in

reproducibility of goniometric measurements between left and right leg, and the use of two

different positioning devices.

4.2.2.1 Learning effect

In order to assess whether there is learning effect in knee flexion measurements, the results

of inter-observer reproducibility of the first and second measuring day are compared in

Table 26. Again, only the results of the observers O1 and O2 were used, because a learning

effect was considered unlikely for those observers who measured only five subjects.


Comparison of the first and second measuring day in Table 26 did not show any

improvement in reproducibility. On the contrary, there was a slight decrease in agreement

and reliability between the first and second measuring day, although the SDD did not

exceed 9° for both measuring days.

Position Reproducibility t1 Reproducibility t2

mD ± SD (°) LOA (°) ICC [95% CI] mD ± SD (°) LOA (°) ICC [95% CI]

P1 1.0 ± 2.5 -4.0 to 5.9 0.99 [0.98 to 0.99] 1.0 ± 3.4 -5.6 to 7.6 0.98 [0.96 to 0.99]

P2 -1.1 ± 3.6 -8.2 to 6.0 0.88 [0.77 to 0.93] 1.1 ± 4.1 -6.9 to 9.0 0.85 [0.84 to 0.96]

Table 26: Flexion - Inter-observer reproducibility of first and second measuring day

4.2.2.2 Positioning devices

Two different positioning devices were used to fix the lower extremities of the subjects in

a standardised knee position, which may contribute to measurement error. The Bland and

Altman plots in Figure 34 show that the differences between observers for both positioning

devices are strictly separated for test position P1, while they are distributed over the range

of mean flexion for test position P2. Further, the differences between observers lie in a

narrower range for positioning device PD1 than for PD2.

85 95 105 115 125 135 145

-10

-5

0

5

10


Dif

fere

nce

O1

-O2

(°)

Mean

1.0

-1.96 SD

-4.0

+1.96 SD

5.9

PD1

PD2

65 70 75 80 85 90 95 100

-15

-10

-5

0

5

10


Dif

fere

nce

O1

-O2

(°)

Mean

-1.1

-1.96 SD

-8.2

+1.96 SD

6.0

PD1

PD2

Figure 34: Influence of different positioning devices

This might be explained by the different construction of the positioning devices. In

positioning device PD1, the leg was laid on two support plates positioned at a certain angle

to each other, which defined the knee joint angle. These angles were approximately 70° for

test position P1 and approximately 90° for test position P2. Conversely, the subjects were

sitting in the positioning device PD2 and the distance between subject´s buttocks and foot

plate defined the angle between thigh and limb. Thus, the knee joint angle far more


depended on the height of the subject, resulting in a broader range of flexion angles than

for positioning device PD1.

Considering differences in agreement between the different positioning devices,

Table 27 shows there was hardly any difference in intra-observer agreement between

positioning devices. Intra-observer agreement (SDD) ranged from 7.5 to 8.5° for PD1 and

5.9 to 8.5° for PD2. However, inter-observer agreement was higher for positioning device

PD1 than PD2 (SDD range, 4.5 to 8.4° and 6.6 to 11.5°, respectively).

Agreement

PD1 PD2

P1 P2 P1 P2

mD ± SD SDD mD ± SD SDD mD ± SD SDD mD ± SD SDD

Inter-observer t1 -0.1 ± 2.2 4.5 -0.8 ± 3.9 8.4 2.0 ± 2.4 6.6 -1.4 ± 3.5 8.2

t2 0.4 ± 3.4 7.0 0.6 ± 2.5 5.6 1.5 ± 3.4 8.1 1.5 ± 5.1 11.5

Intra-observer O1 -1.9 ± 2.9 7.5 -3.0 ± 2.4 7.7 -1.7 ± 2.7 7.0 -3.5 ± 2.2 7.8

O2 -1.3 ± 3.2 7.5 -1.4 ± 3.6 8.5 -2.4 ± 3.1 8.5 -0.2 ± 2.9 5.9

Table 27: Agreement for the positioning devices PD1 and PD2

4.2.2.3 Left vs. right leg

For statistical analysis, both legs were treated as independent entities because it was

hypothesised that there was no difference in reproducibility of the goniometric assessment

of left and right knee flexion. To test this assumption, the SDD and ICC values of left and

right lower extremity were compared. It was found that agreement (SDD) and reliability

(ICC) of left and right leg measurements differed substantially for inter-observer and intra-

observer comparisons, with the right leg showing higher agreement and reliability (Table

28). These results indicate that reproducibility of goniometric measurements using a short-

arm goniometer may be influenced by the handedness of the observers.

Left leg Right leg

SDD range (°) ICC range SDD range (°) ICC range

t1 5.1 to 9.7 0.84 to 0.99 6.7 0.92 to 0.99

t2 6.8 to 9.3 0.86 to 0.99 8.4 to 9.0 0.86 to 0.98

O1 6.5 to 8.8 0.89 to 0.99 6.5 to 7.9 0.92 to 0.98

O2 7.1 to 7.2 0.88 to 0.98 7.4 to 9.0 0.87 to 0.97

Table 28: Flexion – Left and right leg side differences

Discussion - Discussion of the statistical methods 79

4.3 Discussion of the statistical methods

In intra-observer comparison of the goniometric measurements, the SDD (maximum LOA)

and the ICC did not behave the way they were expected, i.e. the higher the SDD, the lower

the ICC and vice versa (Table 12). Even though the SDD was 7.1° for the measurements of

observer O1 at P1 and observer O2 at P2, the ICC values differed substantially (0.98 and

0.89, respectively) (Figure 35). How can these unexpected results be explained?

90 100 110 120 130 140

90

95

100

105

110

115

120

125

130

135

Flexion at P1 at t2 (O1) (°)

Fle

xio

n a

t P

1 a

t t1

(O

1)

(°)

l

r

60 65 70 75 80 85 90 95 100 105 110

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-0.8

-1.96 SD

-7.1

+1.96 SD

5.6

l

r

70 75 80 85 90 95 100

70

75

80

85

90

95

100

Flexion at P2 at t2 (O2) (°)

Fle

xio

n a

t P

2 a

t t1

(O

2)

(°)

l

r

Figure 35: B-A plots vs. scatter plots

The ICC depends on the range of variables measured, which is not the case for the Bland

and Altman LOA [58]. Therefore, for a group of subjects with a wide range of

measurements, the ICC is likely to be greater than for a more homogenous sample group

with similar flexion measurements. This is stated as a major criticism of the ICC on the

one hand. On the other hand, it has been suggested that reliability should reflect true

variability. In this context, a measurement error of 10° may or may not be important

depending on the range of measured flexion values [63].

In case of the measurements obtained by observer O1 at test position P1, the measurement

ranged from 90 to 138° (max-min=48°), which was a much wider range than in the case of

80 90 100 110 120 130 140 150

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-1.8

-1.96 SD

-7.1

+1.96 SD

3.5

l

r

ICC=0.98

ICC=0.87

Discussion - Clinical course 80

observer O2 measuring test position P2 (68 to 99.3°, max-min=31.3°). Thus, an SDD of

7.1° seems to be more relevant clinically in the second case. This is reflected by the

corresponding ICC values, being 0.87 for the second and 0.98 for the first case. Figure 35

compares Bland and Altman plots and scatter diagrams for both cases.

One of the advantages of the B-A limits of agreement, compared to the ICC, is that the

amount of measurement error is quantified in units of the measurement scale, which

simplifies the clinical interpretation of results. However, the Bland and Altman 95% limits

of agreement indicate a range of error, but this must be interpreted with reference to the

range of measurement values obtained. Thus, for a measuring device to be of clinical

value, it has to show small limits of agreements and a high ICC. A statistical measure

taking into account the advantages of ICC and the LOA would be appreciable.

4.4 Clinical course

Lower limb swelling occurred in all patients after TKA surgery. The circumference change

was significantly higher above the knee (PP, mean 5.1 cm, range, 2.3 to 7.6 cm) than at

mid-patella (MP, mean 3.8 cm, range, 1.9 to 9.8 cm) and below the knee (DP) (mean 2.8

cm, range, 1.7 to 7.2 cm) (P=0.0002 and P<0.0001, respetively). The mean maximum

swelling was reached on the third or fourth postoperative day. The findings of this study

are in agreement with the results of Gao et al. (2011), who retrospectively analysed the

mean changes in limb circumferences of 286 patients who underwent primary unilateral

total knee arthroplasty [2]. They reported that swelling was most pronounced from the

third to the fifth post-operative day and usually occurred in both lower limbs. Further

swelling was significantly more pronounced in the operated limb than in the non-operated

limb. The swelling above the knee was also significantly greater than that below the knee.

Passive ROM increased continuously after TKA. On sixth postoperative day, the mean

passive ROM was 79.0° (range, 55 to 100°). Swelling and passive ROM did not show any

significant correlation (P≥0.1375).

Postsurgical pain intensity reported by the patients was highest preoperatively (mean

NRSmax 7.0, range 4 to 9), which might be explained by the patient-controlled analgesia

(72 hours postoperatively). After surgery, the pain intensity decreased from the first

postoperative day (mean NRSmax 6.6, range, 3 to 9) to the dismissal day (mean NRSmax 3.0,

range 1 to 9). The minimum NRS curve showed a course similar to the maximum NRS

curve, except for a very small increase at first postoperative day, indicating that the

minimum pain increased for a short period after surgery.

Conclusion 81

5 Conclusion

In this study it was demonstrated that the reproducibility of lower extremity girth

measurements depends on the sites where the measurements are taken, and the types of

tape measures used. Based on the results of inter-and intra-observer agreement, the

smallest detectable differences (SDD) would lie between 0.4 cm and 2.1 cm. This means

that only changes in girth larger than these values can be detected beyond measurement

error when one or different clinicians perform girth measurements in the knee region in a

comparable environment. Considering the measurement sites, the inter-observer and intra-

observer reproducibility increased from proximal to distal. Regarding the different tape

measures, the Gulick II plus tape measure showed lowest reproducibility. Agreement was

highest for the Waegener tape measure, even though differences to the Gulick I and

standard tape measure were small. If subjects are assessed with the Gulick II plus tape

measure at 7 cm proximal of mid-patella, differences in girth of less than 2.1 cm cannot be

distinguished from measurement error. Conversely, a change in girth of more than 1.2 cm,

1.3 and 1.7 cm measured with the Waegener, Gulick I and standard tape measure,

respectively, can be considered a real change beyond measurement error. However, these

values clearly exceeded the a priori criterion of 1 cm and thus seem to be too large for the

measurement of individual patients in clinical practice, or to assess intra-individual

changes in girth over time.

The results of the knee flexion measurements with a short-arm universal goniometer

showed that changes in flexion exceeding 9° can be considered a real change above

measurement error.

Since the measurements were already standardized and the mean values of multiple

measurements at each timepoint were used for analysis, the best way to reduce variation in

measurements would seem to be training of the observers. In general, intra-observer

reproducibility was reported higher than inter-observer reproducibility, so it is

recommended that the same observer should be responsible for the measurement of

treatment outcome for each patient.

To be useful for outcome assessment in clinical practice or research, an instrument should

have high responsiveness, which is strongly determined by the level of agreement. The

smallest detectable difference should be smaller than the minimal clinically important

difference that one wants to detect. Given the large SDDs, the value of circumferential

girth and goniometric measurements as an outcome measure can be questioned.

Conclusion 82

Clinical evaluation of in-patients undergoing TKA showed that postoperative swelling

does not seem to influence passive ROM after surgery.

References 83

6 References

[1] Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, Gomez-Barrena E, et al.

International survey of primary and revision total knee replacement. Int Orthop 2011

Dec;35(12):1783-1789.

[2] Gao FQ, Li ZJ, Zhang K, Huang D, Liu ZJ. Risk factors for lower limb swelling after

primary total knee arthroplasty. Chin Med J (Engl) 2011 Dec;124(23):3896-3899.

[3] Munk S, Jensen NJ, Andersen I, Kehlet H, Hansen TB. Effect of compression therapy

on knee swelling and pain after total knee arthroplasty. Knee Surg Sports Traumatol

Arthrosc 2013 Feb;21(2):388-392.

[4] Jakobsen TL, Christensen M, Christensen SS, Olsen M, Bandholm T. Reliability of

knee joint range of motion and circumference measurements after total knee arthroplasty:

does tester experience matter? Physiother Res Int 2010 Sep;15(3):126-134.

[5] Lenssen AF, van Dam EM, Crijns YH, Verhey M, Geesink RJ, van den Brandt PA, et

al. Reproducibility of goniometric measurement of the knee in the in-hospital phase

following total knee arthroplasty. BMC Musculoskelet Disord 2007 Aug 17;8:83.

[6] Statistik Austria editor. Jahrbuch der Gesundheitsstatistik 2011. Wien: Verlag

Österreich; 2012.

[7] Van Manen MD, Nace J, Mont MA. Management of primary knee osteoarthritis and

indications for total knee arthroplasty for general practitioners. J Am Osteopath Assoc

2012 Nov;112(11):709-715.


Österreich; 2001.


Österreich; 2002.


Österreich; 2003.

References 84


Österreich; 2005.


Österreich; 2006.


Österreich; 2006.


Österreich; 2007.


Österreich; 2008.


Österreich; 2009.


Österreich; 2010.


Österreich; 2011.

[19] Thomsen MG, Husted H, Otte KS, Orsnes T, Troelsen A. Indications for knee

arthroplasty have remained consistent over time. Dan Med J 2012 Aug;59(8):A4492.

[20] Guyton JL. Arthroplasty of ankle and knee. In: Calale STH, Campbell WCB,

Crenshaw AHH, editors. Campbell's operative orthopaedics. 9. ed. ed. St. Louis, Mo. u.a.]:

Mosby; 1998. p. 232-295.

[21] Leopold SS. Minimally invasive total knee arthroplasty for osteoarthritis. N Engl J

Med 2009 Apr 23;360(17):1749-1758.

[22] Long W, Scuderi G. Total knee replacement. In: Bulstrode C, Wilson-MacDonald J,

Eastwood D, MacMaster J, Fairbank J, Singh P, et al, editors. Oxford Textbook of trauma

and orthopaedics. 2nd ed. New York: Oxford University Press; 2011. p. 660-664.

References 85

[23] Gopinath P, Arun B. Surgical exposures for primary total knee arthroplasty. Journal of

Orthopaedics 1998;1(1):e6.

[24] Kohn D, Pohlemann T. Bikonyläre Prothese und Totalendoprothese. In: Kohn D,

Pohlemann T, editors. Operationsatlas für die orthopädisch-unfallchirurgische

Weiterbildung Berlin Heidelberg: Springer; 2010. p. 109-114.

[25] Jones B. Complications of total knee replacement. In: Bulstrode CJK, editor. Oxford

textbook of trauma and orthopaedics. 2. ed. ed. Oxford: Oxford Univ. Press; 2011. p. 665-

671.

[26] Leone JM, Hanssen AD. Management of Infection at the Site of a Total Knee

Arthroplasty. The Journal of Bone & Joint Surgery 2005 October 1;87(10):2335-2348.

[27] Bauer TW, Parvizi J, Kobayashi N, Krebs V. Diagnosis of Periprosthetic Infection.

The Journal of Bone & Joint Surgery 2006 April 1;88(4):869-882.

[28] Jamsen E, Huhtala H, Puolakka T, Moilanen T. Risk factors for infection after knee

arthroplasty. A register-based analysis of 43,149 cases. J Bone Joint Surg Am 2009

Jan;91(1):38-47.

[29] Kim YH, Kim JS. Incidence and natural history of deep-vein thrombosis after total

knee arthroplasty. A prospective, randomised study. J Bone Joint Surg Br 2002

May;84(4):566-570.

[30] Blanchard J, Meuwly JY, Leyvraz PF, Miron MJ, Bounameaux H, Hoffmeyer P, et al.

Prevention of deep-vein thrombosis after total knee replacement. Randomised comparison

between a low-molecular-weight heparin (nadroparin) and mechanical prophylaxis with a

foot-pump system. J Bone Joint Surg Br 1999 Jul;81(4):654-659.

[31] Martin GM, Thornhill TS, Katz JN. Complications in total knee arthroplasty. In:

Basow DS, editor. UpToDate Waltham, MA: UpToDate; 2013.

[32] Long WJ, Scuderi GR. Total knee replacement. In: Bulstrode CJK, editor. Oxford

textbook of trauma and orthopaedics. 2. ed. ed. Oxford: Oxford Univ. Press; 2011. p. 660-

664.

References 86

[33] Scott RD, 1943-. Totale Kniearthroplastik. 1. Aufl. ed. München ; Jena: Elsevier,

Urban & Fischer; 2007.

[34] Dennis DA, Komistek RD, Stiehl JB, Walker SA, Dennis KN. Range of motion after

total knee arthroplasty: the effect of implant design and weight-bearing conditions. J

Arthroplasty 1998 Oct;13(7):748-752.

[35] Lavernia C, D'Apuzzo M, Rossi MD, Lee D. Accuracy of knee range of motion

assessment after total knee arthroplasty. J Arthroplasty 2008 Sep;23(6 Suppl 1):85-91.

[36] Scott RD. Stiffness associated with total knee arthroplasty. Orthopedics 2009

Sep;32(9):10.3928/01477447-20090728-30.

[37] Sehat KR, Evans R, Newman JH. How much blood is really lost in total knee

arthroplasty?. Correct blood loss management should take hidden loss into account. Knee

2000 Jul 1;7(3):151-155.

[38] Li B, Wen Y, Wu H, Qian Q, Lin X, Zhao H. The effect of tourniquet use on hidden

blood loss in total knee arthroplasty. Int Orthop 2009 Oct;33(5):1263-1268.

[39] te Slaa A, Mulder P, Dolmans D, Castenmiller P, Ho G, van der Laan L. Reliability

and reproducibility of a clinical application of a simple technique for repeated

circumferential leg measurements. Phlebology 2011 Feb;26(1):14-19.

[40] Deltombe T, Jamart J, Recloux S, Legrand C, Vandenbroeck N, Theys S, et al.

Reliability and limits of agreement of circumferential, water displacement, and

optoelectronic volumetry in the measurement of upper limb lymphedema. Lymphology

2007 Mar;40(1):26-34.

[41] Rabe E, Stucker M, Ottillinger B. Water displacement leg volumetry in clinical

studies-a discussion of error sources. BMC Med Res Methodol 2010 Jan 13;10:5-2288-10-

5.

[42] "Archimedes' Principle." Merriam-Webster.com. Merriam-Webster, n.d. Web.

Available at: <http://www.merriam-webster.com/dictionary/Archimedes' principle>.

Accessed August, 22, 2013.

References 87

[43] Tewari N, Gill PG, Bochner MA, Kollias J. Comparison of volume displacement

versus circumferential arm measurements for lymphoedema: implications for the SNAC

trial. ANZ J Surg 2008 Oct;78(10):889-893.

[44] Naylor JM, Ko V, Adie S, Gaskin C, Walker R, Harris IA, et al. Validity and

reliability of using photography for measuring knee range of motion: a methodological

study. BMC Musculoskelet Disord 2011 Apr 18;12:77-2474-12-77.

[45] Cleffken B, van Breukelen G, Brink P, van Mameren H, Olde Damink S. Digital

goniometric measurement of knee joint motion. Evaluation of usefulness for research

settings and clinical practice. Knee 2007 Oct;14(5):385-389.

[46] Norkin CC, White DJ. Introduction to goniometry. Measurement of joint motion; a

guide to goniometry. 3. ed. ed. Philadelphia: Davis; 2003. p. 1-53.

[47] Gogia PP, Braatz JH, Rose SJ, Norton BJ. Reliability and validity of goniometric

measurements at the knee. Phys Ther 1987 Feb;67(2):192-195.

[48] Watkins MA, Riddle DL, Lamb RL, Personius WJ. Reliability of goniometric

measurements and visual estimates of knee range of motion obtained in a clinical setting.

Phys Ther 1991 Feb;71(2):90-6; discussion 96-7.

[49] Ferreira-Valente MA, Pais-Ribeiro JL, Jensen MP. Validity of four pain intensity

rating scales. Pain 2011 Oct;152(10):2399-2404.

[50] Williamson A, Hoggart B. Pain: a review of three commonly used pain rating scales. J

Clin Nurs 2005 Aug;14(7):798-804.

[51] Jensen MP, Chen C, Brugger AM. Postsurgical pain outcome assessment. Pain 2002

Sep;99(1-2):101-109.

[52] Bijur PE, Latimer CT, Gallagher EJ. Validation of a verbally administered numerical

rating scale of acute pain for use in the emergency department. Acad Emerg Med 2003

Apr;10(4):390-392.

[53] Bruton A, Conway JH, Holgate ST. Reliability: What is it, and how is it measured?

Physiotherapy 2000 02/01;86(2):94-99.

References 88

[54] Bravo G, Potvin L. Estimating the reliability of continuous measures with Cronbach's

alpha or the intraclass correlation coefficient: toward the integration of two traditions. J

Clin Epidemiol 1991;44(4-5):381-390.

[55] Scholtes VA, Terwee CB, Poolman RW. What makes a measurement instrument valid

and reliable? Injury 2011 Mar;42(3):236-240.

[56] Atkinson G, Nevill AM. Statistical methods for assessing measurement error

(reliability) in variables relevant to sports medicine. Sports Med 1998 Oct;26(4):217-238.

[57] Weir JP. Quantifying test-retest reliability using the intraclass correlation coefficient

and the SEM. J Strength Cond Res 2005 Feb;19(1):231-240.

[58] De Vet H. Observer Reliability and Agreement. In: Armitage P, Colton T, editors.

Encyclopedia of Biostatistics. 2nd ed.: John Wiley & Sons, Ltd; 2005. p. 3801-3805.

[59] de Vet HC, Terwee CB, Knol DL, Bouter LM. When to use agreement versus

reliability measures. J Clin Epidemiol 2006 Oct;59(10):1033-1039.

[60] Bland JM, Altman DG. Applying the right statistics: analyses of measurement studies.

Ultrasound Obstet Gynecol 2003 Jul;22(1):85-93.

[61] de Vet HC, Bouter LM, Bezemer PD, Beurskens AJ. Reproducibility and

responsiveness of evaluative outcome measures. Theoretical considerations illustrated by

an empirical example. Int J Technol Assess Health Care 2001 Fall;17(4):479-487.

[62] Terwee CB, de Winter AF, Scholten RJ, Jans MP, Deville W, van Schaardenburg D,

et al. Interobserver reproducibility of the visual estimation of range of motion of the

shoulder. Arch Phys Med Rehabil 2005 Jul;86(7):1356-1361.

[63] Rankin G, Stokes M. Reliability of assessment tools in rehabilitation: an illustration of

appropriate statistical analyses. Clin Rehabil 1998 Jun;12(3):187-199.

[64] Allison SC, Westphal KA, Finstuen K. Knee extension and flexion torque as a

function of thigh asymmetry. J Orthop Sports Phys Ther 1993 Dec;18(6):661-666.

References 89

[65] Berard A, Zuccarelli F. Test-retest reliability study of a new improved Leg-O-meter,

the Leg-O-meter II, in patients suffering from venous insufficiency of the lower limbs.

Angiology 2000 Sep;51(9):711-717.

[66] Gross MT, McGrain P, Demilio N, Plyler L. Relationship between multiple predictor

variables and normal knee torque production. Phys Ther 1989 Jan;69(1):54-62.

[67] Harrelson GL, Leaver-Dunn D, Fincher AL, Leeper JD. Inter- and intratester

reliability of lower extremity circumference measurements. Journal of Sport

Rehabilitation, J Sport Rehabil 1998;7(4):300-306.

[68] Kirwan JR, Byron MA, Winfield J, Altman DG, Gumpel JM. Circumferential

measurements in the assessment of synovitis of the knee. Rheumatol Rehabil 1979

May;18(2):78-84.

[69] Labs KH, Tschoepl M, Gamba G, Aschwanden M, Jaeger KA. The reliability of leg

circumference assessment: a comparison of spring tape measurements and optoelectronic

volumetry. Vasc Med 2000;5(2):69-74.

[70] Nicholas JJ, Taylor FH, Buckingham RB, Ottonello D. Measurement of

circumference of the knee with ordinary tape measure. Ann Rheum Dis 1976

Jun;35(3):282-284.

[71] Ross M, Worrell TW. Thigh and calf girth following knee injury and surgery. J

Orthop Sports Phys Ther 1998 Jan;27(1):9-15.

[72] Soderberg GL, Ballantyne BT, Kestel LL. Reliability of lower extremity girth

measurements after anterior cruciate ligament reconstruction. Physiother Res Int

1996;1(1):7-16.

[73] Whitney S, Mattlocks L, Irrgang J. Reliability of lower girth measurements and right-

and left-side differences. Journal of Sport Rehabilitation, J Sport Rehabil 1995;4(2):108-

115.

[74] Brosseau L, Tousignant M, Budd J, Chartier N, Duciaume L, Plamondon S, et al.

Intratester and intertester reliability and criterion validity of the parallelogram and

References 90

universal goniometers for active knee flexion in healthy subjects. Physiother Res Int

1997;2(3):150-166.

[75] Brosseau L, Balmer S, Tousignant M, O'Sullivan JP, Goudreault C, Goudreault M, et

al. Intra- and intertester reliability and criterion validity of the parallelogram and universal

goniometers for measuring maximum active knee flexion and extension of patients with

knee restrictions. Arch Phys Med Rehabil 2001 Mar;82(3):396-402.

[76] Clapper MP, Wolf SL. Comparison of the reliability of the Orthoranger and the

standard goniometer for assessing active lower extremity range of motion. Phys Ther 1988

Feb;68(2):214-218.

[77] Edwards JZ, Greene KA, Davis RS, Kovacik MW, Noe DA, Askew MJ. Measuring

flexion in knee arthroplasty patients. J Arthroplasty 2004 Apr;19(3):369-372.

[78] Kafer W, Fraitzl CR, Kinkel S, Clessienne CB, Puhl W, Kessler S. Outcome

assessment in total knee arthroplasty: is the clinical measurement of range of motion a

reliable measurable outcome variable? Z Orthop Ihre Grenzgeb 2005 Jan-Feb;143(1):25-

29.

[79] Peters PG, Herbenick MA, Anloague PA, Markert RJ, Rubino LJ,3rd. Knee range of

motion: reliability and agreement of 3 measurement methods. Am J Orthop (Belle Mead

NJ) 2011 Dec;40(12):E249-52.

[80] Piriyaprasarth P, Morris ME, Winter A, Bialocerkowski AE. The reliability of knee

joint position testing using electrogoniometry. BMC Musculoskelet Disord 2008 Jan

22;9:6-2474-9-6.

[81] Rheault W, Miller M, Nothnagel P, Straessle J, Urban D. Intertester reliability and

concurrent validity of fluid-based and universal goniometers for active knee flexion. Phys

Ther 1988 Nov;68(11):1676-1678.

[82] Rothstein JM, Miller PJ, Roettger RF. Goniometric reliability in a clinical setting.

Elbow and knee measurements. Phys Ther 1983 Oct;63(10):1611-1615.

[83] Alonso A, Hekeik P, Adams R. Predicting a recovery time from the initial assessment

of a quadriceps contusion injury. Aust J Physiother 2000;46(3):167-177.

References 91

[84] Marks JS, Palmer MK, Burke MJ, Smith P. Observer variation in examination of knee

joints. Ann Rheum Dis 1978 Aug;37(4):376-377.

[85] Theiler R, Stucki G, Schutz R, Hofer H, Seifert B, Tyndall A, et al. Parametric and

non-parametric measures in the assessment of knee and hip osteoarthritis: interobserver

reliability and correlation with radiology. Osteoarthritis Cartilage 1996 Mar;4(1):35-42.

[86] Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychol

Bull 1979 Mar;86(2):420-428.

[87] IBM Corp. IBM SPSS Statistics for Windows, Version 20.0. Released 2011. IBM

Corp., Armonk, NY

[88] MedCalc Software. MedCalc for Windows version 12.7.0. MedCalc Software,

Ostend, Belgium

[89] Bland JM, Altman DG. Statistical methods for assessing agreement between two

methods of clinical measurement. Lancet 1986 Feb 8;1(8476):307-310.

[90] Hanneman SK. Design, analysis, and interpretation of method-comparison studies.

AACN Adv Crit Care 2008 Apr-Jun;19(2):223-234.

[91] Microsoft. Microsoft Office Excel. 2010. Microsoft, Redmond, USA

[92] Baker SG, Roush JK, Unis MD, Wodiske T. Comparison of four commercial devices

to measure limb circumference in dogs. Vet Comp Orthop Traumatol 2010;23(6):406-410.

[93] Maylia M, Fairclough J, Nokes L, Jones M. Can thigh girth be measured accurately?

A preliminary investigation. Journal of Sport Rehabilitation, J Sport Rehabil 1999;8(1):43-

49.

[94] Geil MD. Consistency and accuracy of measurement of lower-limb amputee

anthropometrics. J Rehabil Res Dev 2005 Mar-Apr;42(2):131-140.

[95] Yoo JH, Yi SR, Kim JH. The geometry of patella and patellar tendon measured on

knee MRI. Surg Radiol Anat 2007 Dec;29(8):623-628.

References 92

[96] Introna F,Jr, Di Vella G, Campobasso CP. Sex determination by discriminant analysis

of patella measurements. Forensic Sci Int 1998 Jul 6;95(1):39-45.

Appendix - Results of the second measuring day 93

A Appendix

A.1 Results of the second measuring day

A.1.1 Inter-observer reproducibility of girth measurements (t2)

Table 29 and Table 30 show the results of the inter-observer agreement and reliability

calculations, respectively, for the second measuring day. The corresponding Bland and

Altman plots for the measurement sites at 7 cm proximal of mid-patella, mid-patella, and 7

cm distal of mid-patella are presented in Figure 36, Figure 37, and Figure 38, respectively.

The SDD ranged from 0.4 to 1.8 cm and was highest for the measurement site at 7 cm

proximal of mid-patella. The Waegener tape measure showed the highest agreement (SDD

range, 0.6 to 1.0 cm), followed by the standard tape measures (SDD range, 0.7 to 1.2 cm)

and the Gulick I tape measure (0.4 to 1.3 cm). As for the first measuring day, the SDD was

highest for the Gulick II plus measure (range, 0.5 to 1.8 cm). The inter-observer reliability

was generally high, with ICCs ranging from 0.94 to 0.99. Again, the lowest reliability was

found for the Gulick II tape measure (ICC range, 0.94 to 0.99)

O1 O2 Agreement t2: O1-O2

Mean ± SD Mean ± SD mD [95% CI] SDdiff Lower limit [95% CI] Upper limit [95% CI]

PP GI 38.8 ± 2.3 38.6 ± 2.5 0.2 [-0.0 to 0.4] 0.6 -1.0 [-1.4 to -0.6] 1.3 [1.0 to 1.7]

GII 40.7 ± 2.4 40.5 ± 2.5 0.2 [-0.1 to 0.5] 0.8 -1.4 [-1.8 to -0.9] 1.8 [1.3 to 2.3]

S 40.3 ± 2.5 40.2 ± 2.6 0.1 [0.0 to 0.3] 0.6 -0.9 [-1.3 to -0.6] 1.2 [0.9 to 1.5]

W 38.8 ± 2.4 38.8 ± 2.6 0.1 [-0.1 to 0.2] 0.5 -0.8 [-1.1 to -0.6] 1.0 [0.7 to 1.2]

MP GI 36.6 ± 2.2 36.6 ± 2.2 0.0 [-0.1 to 0.2] 0.4 -0.8 [-1.1 to -0.5] 0.8 [0.5 to 1.1]

GII 37.6 ± 2.0 37.7 ± 2.1 -0.1 [-0.2 to -0.0] 0.3 -0.8 [-1.0 to -0.6] 0.5 [0.3 to 0.7]

S 37.7 ± 2.0 37.5 ± 2.1 0.2 [0.1 to 0.3] 0.4 -0.5 [-0.7 to -0.3] 0.9 [0.7 to 1.1]

W 37.0 ± 2.0 36.9 ± 2.1 0.1 [0.0 to 0.2] 0.3 -0.5 [-0.6 to -0.3] 0.7 [0.5 to 0.8]

DP GI 33.4 ± 2.3 33.5 ± 2.4 -0.1 [-0.2 to 0.0] 0.3 -0.7 [-0.9 to -0.5] 0.4 [0.2 to 0.6]

GII 34.2 ± 2.2 34.3 ± 2.3 -0.1 [-0.3 to 0.0] 0.4 -0.9 [-1.1 to -0.7] 0.7 [0.4 to 0.9]

S 34.5 ± 2.1 34.4 ± 2.2 0.1 [-0.0 to 0.2] 0.3 -0.5 [-0.7 to -0.3] 0.7 [0.5 to 0.9]

W 34.0 ± 2.1 34.2 ± 2.1 -0.2 [-0.3 to -0.0] 0.4 -0.9 [-1.2 to -0.7] 0.6 [0.4 to 0.8]

Table 29: Girth - Inter-observer agreement on second measuring day (O1 and O2)


Tape ICC [95% CI]

PP MP DP

GI 0.97 [0.93 to 0.99] 0.98 [0.96 to 0.99] 0.99 [0.98 to 1.00]

GII 0.94 [0.89 to 0.97] 0.99 [0.97 to 0.99] 0.98 [0.97 to 0.99]

S 0.98 [0.95 to 0.99] 0.98 [0.95 to 0.99] 0.99 [0.98 to 0.99]

W 0.98 [0.97 to 0.99] 0.99 [0.98 to 0.99] 0.98 [0.96 to 0.99]

Table 30: Girth - Inter-observer reliability (ICC) on second measuring day (O1 and O2)

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth GII at PP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.2

-1.96 SD

-1.4

+1.96 SD

1.8

l

r

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth W at PP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.0 l

r

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth GI at PP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.2

-1.96 SD

-1.0

+1.96 SD

1.3

l

r

34 36 38 40 42 44 46 48

-2

-1

0

1

2

3

Mean girth S at PP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.1

-1.96 SD

-0.9

+1.96 SD

1.2

l

r

Figure 36: Girth - Inter-observer B-A plots at PP for the observers O1 and O2 (t2)

with mean difference between observers O1 and O2 (solid black line) and limits of agreement (broken black lines);


32 34 36 38 40 42 44

-2

-1

0

1

2

3

Mean girth W at MP (t2) (cm)

Dif

fere

nce

O1-O

2 (

cm)

Mean

0.1

-1.96 SD

-0.5

+1.96 SD

0.7l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3

Mean girth S at MP (t2) (cm)D

iffe

ren

ce O

1-O

2 (

cm)

Mean

0.2

-1.96 SD

-0.5

+1.96 SD

0.9 l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3

Mean girth GII at MP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.1-1.96 SD

-0.8

+1.96 SD

0.5

l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3

Mean girth GI at MP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.0

-1.96 SD

-0.8

+1.96 SD

0.8 l

r

Figure 37: Girth - Inter-observer B-A plots at MP for the observers O1 and O2 (t2)

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth S at DP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

0.1-1.96 SD

-0.5

+1.96 SD

0.7l

r

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth W at DP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.2

-1.96 SD

-0.9

+1.96 SD

0.6l

r

Figure 38: Girth - Inter-observer B-A plots at DP for the observers O1 and O2 (t2)

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth GI at DP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.1

-1.96 SD

-0.7

+1.96 SD

0.4

l

r

30 32 34 36 38 40

-2

-1

0

1

2

3

Mean girth GII at DP (t2) (cm)

Dif

fere

nce

O1

-O2

(cm

)

Mean

-0.1

-1.96 SD

-0.9

+1.96 SD

0.7l

r


A.1.2 Inter-observer reproducibility of goniometric measurements (t2)

Table 31 shows the results of the inter-observer reproducibility for the second measuring

day. The corresponding Bland and Altman plots are shown in Figure 39. Reliability and

agreement were higher for the knee joint position P1 than P2. The SDD ranged from 7.6 to

9.0°, and the ICC from 0.85 to 0.98. Inter-observer reproducibility was higher for test

position P1 than P2.

Position O1 (°) O2 (°) Agreement: O1-O2 (°) Reliability

Mean ±SD Mean ±SD mD SDdiff Lower limit Upper limit ICC

[95% CI] [95% CI] [95% CI] [95% CI]

P1 113.8 ±18.04 112.8 ±17.3 1.0 [-0.2 ; 2.1] 3.4 -5.6 [-7.7 ; -3.6] 7.6 [5.5 ; 9.6] 0.98 [0.96 ; 0.99]

P2 84.0 ±6.32 82.4 ±8.3 1.1 [-0.3 ; 2.5] 4.1 -6.9 [-9.3 ; -4.4] 9.0 [6.6 ; 11.5] 0.85 [0.73 ; 0.92]

Table 31: Flexion - Inter-observer reproducibility on second measuring day (O1 and O2)

mD, mean difference between measuring days; sample size, n=19

90 100 110 120 130 140 150

-15

-10

-5

0

5

10

15

Mean flexion at P1 (t2) (°)

Dif

fere

nce

O1

-O2

(°)

Mean

1.0

-1.96 SD

-5.6

+1.96 SD

7.6

l

r

60 70 80 90 100 110

-15

-10

-5

0

5

10

15

Mean flexion at P2 (t2) (°)

Dif

fere

nce

O1

-O2

(°)

Mean

1.1

-1.96 SD

-6.9

+1.96 SD

9.0

l

r

Figure 39: Flexion - Inter-observer B-A plots for second measuring day (O1 and O2)

for the knee joint positions P1 and P2; with mean difference between observers O1 and O2 (solid black line) and limits of

agreement (broken black lines); l, left leg; r, right leg;

Appendix - Results of the observers O1, O2, O3, O4 and O5 97

A.2 Results of the observers O1, O2, O3, O4 and O5

A.2.1 Reproducibility of girth measurements (O1-O5)

A.2.1.1 Inter-observer reliability (O1-O5)

A.2.1.1.1 First measuring day

The inter-observer reliability (ICC) measured by the observers O1, O2, O3, O4 and O5 on

the first measuring day ranged from 0.94 to 0.98 (mean ICC 0.97) across three

measurement sites and four tape measures (Table 32). The ICCs were higher at the mid-

patella site (range, 0.97 to 0.98) than at 7 cm distal of mid-patella (0.97) and 7 cm

proximal of mid-patella (range 0.94 to 0.97). Considering the different measuring tapes,

the ICC values were slightly higher for the Gulick I and Gulick II tape measures (mean

ICC 0.97) than for the standard and Waegener tape measures (mean ICC 0.96).

Comparing these results with those of the observers O1 and O2 measuring 20 subjects,

reliability was slightly lower (mean ICC, 0.98 and 0.97, respectively).

Because the Bland and Altman limits of agreement were designed for pairwise comparison

of measurements, this analysis could not be applied to the data of the five observers for

inter-observer agreement analysis purposes.

Tape Reliability: ICC [95% CI]

PP MP DP

GI 0.96 [0.91 to 0.99] 0.98 [0.94 to 0.99] 0.97 [0.92 to 0.99]

GII 0.97 [0.93 to 0.99] 0.97 [0.94 to 0.99] 0.97 [0.92 to 0.99]

S 0.94 [0.83 to 0.98] 0.98 [0.94 to 0.99] 0.97 [0.91 to 0.99]

W 0.94 [0.83 to 0.99] 0.98 [0.94 to 0.99] 0.97 [0.93 to 0.99]

Table 32: Girth - Inter-observer reliability for the observers O1-O5 (n=10 legs)

A.2.1.1.2 Second measuring day

Table 33 show the results of the reliability analysis for the second measuring day. The ICC

ranged from 0.91 to 0.99 (mean ICC 0.97). Thus, inter-observer reliability was comparable

between the first and second measuring day. Reliability was higher for the measurement

sites at mid-patella (range, 0.97 to 0.98) and 7 cm distal of mid-patella (range 0.98 to 0.99)

than at the measurement site at 7 cm proximal of mid-patella (range 0.91 to 0.98). The

Gulick I tape measure showed the highest reliability (range 0.98 to 0.99), followed by the


Waegener tape measure (range 0.95 to 0.99) and the standard tape measure (range, 0.93 to

0.98). Level of reliability was lowest for the Gulick II plus tape measure (ICC range, 0.91

to 0.98).

Tape ICC [95 CI]

PP MP DP

GI 0.98 [0.94 to 0.99] 0.98 [0.95 to 0.99] 0.99 [0.96 to 1.00]

GII 0.91 [0.74 to 0.97] 0.97 [0.89 to 0.99] 0.98 [0.92 to 0.99]

S 0.93 [0.80 to 0.98] 0.97 [0.92 to 0.99] 0.98 [0.96 to 1.00]

W 0.95 [0.82 to 0.99] 0.98 [0.93 to 0.99] 0.98 [0.95 to 1.00]

Table 33: Girth - Inter-observer reliability (ICC) on second measuring day (O1-O5)

A.2.1.2 Intra-observer reproducibility (O1-O5)

The results of intra-observer agreement for the observers O1, O2, O3, O4, and O5 are

presented in Table 34, Table 35, Table 37 and Table 38, respectively. Table 39 shows the

corresponding intra-observer reliability (ICC).

Tables

Site Tape t1 (cm) t2 (cm) t1-t2 (cm) Lower limit (cm) Upper limit (cm)

Mean ± SD Mean ± SD mD [95% CI] SDdiff [95% CI] [95% CI]

PP GI 38.7 ± 2.7 38.4 ± 2.7 0.3 [0.0 to 0.5] 0.4 -0.5 [-0.9 to 0.0] 1.0 [0.5 to 1.5]

GII 40.2 ± 2.8 39.9 ± 2.8 0.3 [-0.1 to 0.8] 0.6 -0.9 [-1.7 to -0.1] 1.5 [0.7 to 2.3]

S 39.8 ± 3.0 39.6 ± 2.8 0.3 [0.0 to 0.5] 0.4 -0.4 [-0.9 to 0.0] 1.0 [0.5 to 1.4]

W 38.7 ± 2.9 38.5 ± 2.8 0.2 [-0.1 to 0.4] 0.3 -0.5 [-0.9 to -0.0] 0.9 [0.4 to 1.3]

MP GI 37.2 ± 2.5 36.9 ± 2.5 0.3 [0.1 to 0.4] 0.2 -0.1 [-0.4 to 0.1] 0.7 [0.4 to 1.0]

GII 38.0 ± 2.7 37.8 ± 2.5 0.2 [0.0 to 0.4] 0.3 -0.4 [-0.7 to 0.0] 0.8 [0.4 to 1.2]

S 38.0 ± 2.6 37.7 ± 2.4 0.3 [0.0 to 0.5] 0.3 -0.4 [-0.8 to 0.0] 0.9 [0.5 to 1.3]

W 37.5 ± 2.4 37.3 ± 2.3 0.2 [-0.1 to 0.4] 0.4 -0.5 [-0.9 to -0.0] 0.9 [0.4 to 1.3]

DP GI 34.2 ± 2.4 33.8 ± 2.7 0.3 [0.1 to 0.6] 0.3 -0.3 [-0.8 to 0.1] 1.0 [0.6 to 1.4]

GII 35.0 ± 2.5 34.7 ± 2.7 0.3 [0.0 to 0.6] 0.4 -0.5 [-1.1 to -0.0] 1.1 [0.6 to 1.6]

S 35.1 ± 2.5 34.8 ± 2.7 0.3 [0.1 to 0.5] 0.3 -0.3 [-0.7 to 0.1] 0.9 [0.5 to 1.2]

W 34.7 ± 2.3 34.4 ± 2.6 0.3 [0.0 to 0.5] 0.3 -0.4 [-0.8 to 0.0] 0.9 [0.5 to 1.3]

Table 34: Girth - Intra-observer agreement of observer O1 (n=10 legs)




PP GI 38.5 ± 2.9 38.3 ± 2.9 0.2 [-0.2 to 0.7] 0.6 -1.0 [-1.7 to -0.2] 1.4 [0.7 to 2.2]

GII 40.1 ± 2.8 39.7 ± 2.9 0.5 [0.1 to 0.8] 0.5 -0.5 [-1.1 to 0.1] 1.4 [0.8 to 2.0]

S 39.6 ± 2.8 39.5 ± 2.9 0.1 [-0.3 to 0.5] 0.6 -1.1 [-1.9 to -0.3] 1.3 [0.5 to 2.1]

W 38.6 ± 2.8 38.3 ± 2.9 0.3 [0.0 to 0.5] 0.4 -0.4 [-0.9 to 0.0] 1.0 [0.5 to 1.4]

MP GI 37.0 ± 2.5 37.0 ± 2.6 0.0 [-0.3 to 0.3] 0.4 -0.8 [-1.3 to -0.3] 0.7 [0.2 to 1.3]

GII 38.0 ± 2.4 38.0 ± 2.5 0.1 [-0.2 to 0.3] 0.3 -0.6 [-1.0 to -0.2] 0.7 [0.3 to 1.2]

S 37.9 ± 2.4 37.7 ± 2.5 0.1 [0.0 to 0.3 ] 0.2 -0.3 [-0.6 to -0.0] 0.6 [0.3 to 0.9]

W 37.4 ± 2.1 37.3 ± 2.2 0.2 [- 0.1 to 0.4] 0.3 -0.4 [-0.8 to -0.0] 0.7 [0.4 to 1.1]

DP GI 34.1 ± 2.5 34.1 ± 2.7 0.0 [-0.3 to 0.3] 0.4 -0.8 [-1.3 to -0.3] 0.7 [0.3 to 1.2]

GII 34.9 ± 2.5 34.8 ± 2.8 0.1 [-0.1 to 0.4] 0.4 -0.6 [-1.0 to -0.1] 0.8 [0.4 to 1.3]

S 34.9 ± 2.4 34.9 ± 2.6 0.0 [-0.2 to 0.2] 0.2 -0.4 [-0.7 to -0.1] 0.5 [0.2 to 0.8]

W 34.9 ± 2.4 34.7 ± 2.4 0.2 [-0.1 to 0.5] 0.5 -0.7 [-1.3 to -0.1] 1.1 [0.5 to 1.7]



Mean ± SD Mean ±SD mD [95% CI] SDdiff [95% CI] [95% CI]

PP GI 38.1 ± 2.8 37.9 ± 2.8 0.2 [-0.2 to 0.6] 0.5 -0.9 [-1.5 to -0.2] 1.2 [0.6 to 1.9]

GII 39.6 ± 3.1 38.6 ± 2.9

1.0 [0.2 to 1.9] 1.2 -1.3 [-2.8 to 0.2] 3.3 [1.8 to 4.8]

S 40.0 ± 3.0 39.4 ± 2.7

0.6 [0.2 to 1.0] 0.6 -0.6 [-1.4 to 0.2] 1.8 [1.0 to 2.5]

W 39.0 ± 2.9 38.8 ± 2.6

0.3 [-0.2 to 0.8] 0.7 -1.1 [-2.1 to -0.2] 1.7 [0.8 to 2.7]

MP GI 36.7 ± 2.6 36.5 ± 2.5 0.1 [-0.2 to 0.5] 0.5 -0.8 [-1.5 to -0.2] 1.1 [0.5 to 1.8]

GII 37.6 ± 2.6 37.1 ± 2.5

0.4 [0.0 to 0.9] 0.6 -0.7 [-1.4 to 0.0] 1.6 [0.9 to 2.38]

S 37.7 ± 2.6 37.3 ± 2.4

0.3 [-0.1 to 0.7] 0.5 -0.7 [-1.4 to -0.0] 1.3 [0.7 to 2.08]

W 37.5 ± 2.5 37.1 ± 2.2

0.3 [-0.1 to 0.8] 0.6 -0.9 [-1.7 to -0.1] 1.5 [0.7 to 2.3]

DP GI 33.8 ± 2.7 33.6 ± 2.6 0.2 [-0.1 to 0.6] 0.5 -0.8 [-1.4 to -0.1] 1.2 [0.6 to 1.9]

GII 34.5 ± 2.8 34.2 ± 2.6

0.4 [0.0 to 0.7] 0.5 -0.6 [-1.2 to 0.0] 1.3 [0.7 to 2.0]

S 34.6 ± 2.8 34.4 ± 2.3

0.2 [-0.3 to 0.7] 0.7 -1.1 [-1.9 to -0.2] 1.5 [0.7 to 2.4]

W 34.8 ± 2.6 34.7 ± 2.4

0.1 [-0.2 to 0.5] 0.5 -0.8 [-1.4 to -0.2] 1.1 [0.5 to 1.7]




mean ± SD mean ±SD mD [95% CI] SDdiff [95% CI] [95% CI]

PP GI 38.4 ± 3.3 38.1 ± 3.1 0.3 [-0.1 to 0.8] 0.6 -0.8 [-1.5 to -0.1] 1.5 [0.7 to 2.2]

GII 40.2 ± 3.4 40.0 ± 3.2 0.3 [-0.3 to 0.8] 0.8 -1.3 [-2.3 to -0.3] 1.8 [0.8 to 2.8]

S 40.6 ± 3.5 40.2 ± 3.5 0.4 [-0.1 to 0.8] 0.6 -0.8 [-1.6 to -0.1] 1.6 [0.8 to 2.3]

W 39.4 ± 3.2 39.0 ± 3.1 0.4 [0.1 to 0.6] 0.4 -0.4 [-0.9 to 0.1] 1.1 [0.6 to 1.6]

MP GI 36.9 ± 2.8 36.8 ± 2.5 0.1 [-0.2 to 0.5] 0.5 -0.8 [-1.4 to -0.2] 1.1 [0.5 to 1.7]

GII 38.1 ± 2.8 37.9 ± 2.6 0.1 [-0.3 to 0.5] 0.5 -0.9 [-1.6 to -0.2] 1.2 [0.5 to 1.8]

S 38.2 ± 3.0 38.0 ± 2.7 0.2 [-0.2 to 0.6] 0.6 -0.9 [-1.6 to -0.2] 1.3 [0.6 to 2.0]

W 37.7 ± 2.6 37.4 ± 2.4 0.3 [0.0 to 0.6] 0.4 -0.4 [-0.9 to 0.0] 1.0 [0.6 to 1.5]

DP GI 34.0 ± 2.7 33.7 ± 2.6 0.2 [-0.0 to 0.4] 0.3 -0.5 [-0.9 to -0.0] 0.9 [0.4 to 1.3]

GII 35.0 ± 2.7 34.8 ± 2.6 0.2 [-0.1 to 0.5] 0.4 -0.7 [-1.2 to -0.1] 1.1[0.5 to 1.6]

S 35.1 ± 2.8 34.8 ± 2.7 0.3 [0.0 to 0.6] 0.4 -0.5 [-1.0 to 0.0] 1.1[0.6 to 1.6]

W 35.2 ± 2.5 35.0 ± 2.3 0.2 [-0.0 to 0.5] 0.3 -0.4 [-0.8 to 0.0] 0.9 [0.5 to 1.3]


Site Tape t1(cm) t2 (cm) t1-t2 (cm) Lower limit (cm) Upper limit (cm)

mean ± SD Mean ±SD mD [95% CI] SDdiff [95% CI] [95% CI]

PP GI 38.5 ± 3.4 38.2 ± 2.7 0.3 [-0.3 to 0.9] 0.8 -1.4 [-2.4 to -0.3] 1.9 [0.8 to 2.9]

GII 40.5 ± 3.4 40.4 ± 2.6 0.0 [-0.9 to 0.9] 1.3 -2.4 [-4.0 to -0.8] 2.5 [0.9 to 4.1]

S 40.9 ± 3.3 40.8 ± 2.8 0.2 [-0.4 to 0.7] 0.8 -1.3 [-2.3 to -0.4] 1.6 [0.7 to 2.6]

W 39.9 ± 3.1 39.6 ± 2.8 0.3 [-0.3 to 0.9] 0.9 -1.4 [-2.5 to -0.3] 2.0 [0.9 to 3.1]

MP GI 37.2 ± 2.7 37.1 ± 2.3 0.1 [-0.3 to 0.5] 0.5 -0.9 [-1.6 to -0.3] 1.1 [0.5 to 1.8]

GII 38.1 ± 2.8 38.0 ± 2.6 0.1 [-0.3 to 0.5] 0.6 -1.0 [-1.7 to -0.3] 1.2 [0.5 to 1.9]

S 38.2 ± 2.7 38.1 ± 2.5 0.1 [-0.1 to 0.3] 0.2 -0.4 [-0.7 to -0.1] 0.6 [0.3 to 0.9]

W 37.8 ± 2.7 37.8 ± 2.5 0.0 [-0.2 to 0.3] 0.3 -0.6 [-1.0 to -0.2] 0.7 [0.3 to 1.1]

DP GI 34.5 ± 2.7 34.0 ± 2.5 0.5 [0.1 to 1.0] 0.6 -0.7 [-1.5 to 0.1] 1.7 [1.0 to 2.5]

GII 35.3 ± 2.8 34.9 ± 2.4 0.4 [-0.2 to 1.0] 0.8 -1.3 [-2.3 to -0.2] 2.0 [1.0 to 3.1]

S 35.4 ± 2.7 34.9 ± 2.7 0.6 [0.0 to 1.1] 0.7 -0.9 [-1.8 to 0.1] 2.0 [1.0 to 2.9]

W 35.0 ± 2.7 34.5 ± 2.5 0.5 [0.0 to 1.0] 0.7 -0.8 [-1.6 to 0.1] 1.8 [1.0 to 2.7]



Site Tape

Reliability t1-t2: ICC [95% CI]

O1 O2 O3 O4 O5

PP GI 0.99 [0.92 to 1.00] 0.98 [0.91 to 0.99] 0.98 [0.93 to 1.00] 0.98 [0.91 to 1.00] 0.96 [0.87 to 0.99]

GII 0.97 [0.89 to 0.99] 0.97 [0.76 to 0.99] 0.88 [0.42 to 0.97] 0.97 [0.89 to 0.99] 0.92 [0.72 to 0.98]

S 0.99 [0.93 to 1.00] 0.98 [0.92 to 0.99] 0.96 [0.64 to 0.99] 0.98 [0.92 to 1.00] 0.97 [0.89 to 0.99]

W 0.99 [0.96 to 1.00] 0.99 [0.92 to 1.00] 0.96 [0.86 to 0.99] 0.99 [0.89 to 1.00] 0.95 [0.84 to 0.99]

MP GI 0.99 [0.80 to 1.00] 0.99 [0.96 to 1.00] 0.98 [0.93 to 1.00] 0.98 [0.94 to 1.00] 0.98 [0.92 to 0.99]

GII 0.99 [0.94 to 1.00] 0.99 [0.97 to 1.00] 0.96 [0.79 to 0.99] 0.98 [0.93 to 1.00] 0.98 [0.93 to .100]

S 0.99 [0.90 to 1.00] 0.99 [0.98 to 1.00] 0.97 [0.88 to 0.99] 0.98 [0.93 to 1.00] 1.00 [0.98 to 1.00]

W 0.99 [0.94 to 1.00] 0.99 [0.96 to 1.00] 0.96 [0.85 to 0.99] 0.98 [0.89 to 1.00] 0.99 [0.97 to 1.00]

DP GI 0.98 [0.81 to 1.00] 0.99 [0.96 to 1.00] 0.98 [0.93to 1.00] 0.99 [0.95 to 1.00] 0.95 [0.70 to 1.00]

GII 0.98 [0.92 to 1.00] 0.98 [0.87 to 0.99] 0.99 [0.96 to 1.00] 0.98 [0.94 to 1.00] 0.94 [0.79 to 0.99]

S 0.99 [0.88 to 1.00] 1.00 [0.99 to 1.00] 0.97 [0.88 to 0.99] 0.98 [0.90 to 1.00] 0.95 [0.73 to 0.99]

W 0.99 [0.90 to 1.00] 0.98 [0.92 to 0.99] 0.98 [0.93 to 1.00] 0.99 [0.94 to 1.00] 0.95 [0.73 to 0.99]

Table 39: Girth - Intra-observer reliability for the observers O1-O5

Bland and Altman plots

The B-A plots for the observers O1, O1, O3, O4 and O5 at the measurement site 7 cm

proximal of mid-patella are shown in Figure 40, Figure 41, Figure 42, Figure 43 and Figure

44, respectively. It has to be taken into account that the scaling of the y-axis changes

differs from observer to observer. In Figure 45, Figure 46, Figure 47, Figure 48 and Figure

49, the B-A plots for the measurement site at mid-patella are presented. Finally, the B-A

plots for the measurement site at 7 cm distal of mid-patella are displayed in Figure 50,

Figure 51, Figure 52, Figure 53 and Figure 54. In these plots, again, the scaling of the y-

axis differs from observer to observer.


32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.5

+1.96 SD

1.0

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

Mean girth GII at PP (O1) (cm)D

iffe

ren

ce t

1-t

2 (

cm)

Mean

0.3

-1.96 SD

-0.9

+1.96 SD

1.5

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.4

+1.96 SD

1.0

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.5

+1.96 SD

0.9

Figure 40: Girth - Intra-observer B-A plots at PP for the observer O1 (n=10 legs)

32 34 36 38 40 42 44 46 48 50 52

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-1.0

+1.96 SD

1.4

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.5

-1.96 SD

-0.5

+1.96 SD

1.4

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-1.1

+1.96 SD

1.3

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.4

+1.96 SD

1.0



32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3

4


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.9

+1.96 SD

1.2

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3

4


iffe

ren

ce t

1-t

2 (

cm)

Mean

1.0

-1.96 SD

-1.3

+1.96 SD

3.3

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3

4


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.6

-1.96 SD

-0.6

+1.96 SD

1.8

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3

4


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-1.1

+1.96 SD

1.7


32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.8

+1.96 SD

1.5

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-1.3

+1.96 SD

1.8

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.4

-1.96 SD

-0.8

+1.96 SD

1.6

32 34 36 38 40 42 44 46 48 50

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.4

-1.96 SD

-0.4

+1.96 SD

1.1



32 34 36 38 40 42 44 46 48 50

-3

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-1.4

+1.96 SD

1.9

32 34 36 38 40 42 44 46 48 50

-3

-2

-1

0

1

2

3


iffe

ren

ce t

1-t

2 (

cm)

Mean

0.0

-1.96 SD

-2.4

+1.96 SD

2.5

32 34 36 38 40 42 44 46 48 50

-3

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-1.3

+1.96 SD

1.6

32 34 36 38 40 42 44 46 48 50

-3

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-1.4

+1.96 SD

2.0


32 34 36 38 40 42

-2

-1

0

1

2

Mean girth GI at MP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3-1.96 SD

-0.1

+1.96 SD

0.7

34 36 38 40 42 44

-2

-1

0

1

2

Mean girth GII at MP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.4

+1.96 SD

0.8

34 36 38 40 42 44

-2

-1

0

1

2

Mean girth S at MP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.4

+1.96 SD

0.9

32 34 36 38 40 42

-2

-1

0

1

2

Mean girth W at MP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.5

+1.96 SD

0.9

Figure 45: Girth - Intra-observer B-A plots at MP for observer O1 (n=10 legs)


32 34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

-0.0

-1.96 SD

-0.8

+1.96 SD

0.7

34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.6

+1.96 SD

0.7

34 36 38 40 42 44

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1-1.96 SD

-0.3

+1.96 SD

0.6

33 34 35 36 37 38 39 40 41

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.4

+1.96 SD

0.7


32 34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.1

32 34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.4

-1.96 SD

-0.7

+1.96 SD

1.6

32 34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.7

+1.96 SD

1.3

34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.9

+1.96 SD

1.5



32 34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.1

34 36 38 40 42 44

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.9

+1.96 SD

1.2

34 36 38 40 42 44

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.9

+1.96 SD

1.3

32 34 36 38 40 42 44

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.4

+1.96 SD

1.0


32 34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.9

+1.96 SD

1.1

30 32 34 36 38 40

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

Mean girth GII at DP (O5) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.39

-1.96 SD

-1.25

+1.96 SD

2.03

34 36 38 40 42 44

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1-1.96 SD

-0.4

+1.96 SD

0.6

34 36 38 40 42

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.0

-1.96 SD

-0.6

+1.96 SD

0.7



30 32 34 36 38 40

-2

-1

0

1

2

Mean girth GI at DP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.3

+1.96 SD

1.0

30 32 34 36 38 40

-2

-1

0

1

2

Mean girth GII at DP (O1) (cm)D

iffe

ren

ce t

1-t

2 (

cm)

Mean

0.3

-1.96 SD

-0.5

+1.96 SD

1.1

30 32 34 36 38 40

-2

-1

0

1

2

Mean girth S at DP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.3

+1.96 SD

0.9

30 32 34 36 38 40

-2

-1

0

1

2

Mean girth W at DP (O1) (cm)

Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.4

+1.96 SD

0.9

Figure 50: Girth - Intra-observer B-A plots at DP for observer O1 (n=10 legs)

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

-0.0

-1.96 SD

-0.8

+1.96 SD

0.7

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.6

+1.96 SD

0.8

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.0-1.96 SD

-0.4

+1.96 SD

0.5

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.7

+1.96 SD

1.1



28 30 32 34 36 38

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.8

+1.96 SD

1.2

30 32 34 36 38 40

-2

-1

0

1

2


iffe

ren

ce t

1-t

2 (

cm)

Mean

0.4

-1.96 SD

-0.6

+1.96 SD

1.3

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-1.1

+1.96 SD

1.5

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.1


28 30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.5

+1.96 SD

0.9

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.7

+1.96 SD

1.1

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.3

-1.96 SD

-0.5

+1.96 SD

1.1

30 32 34 36 38 40

-2

-1

0

1

2


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.4

+1.96 SD

0.9



30 32 34 36 38 40

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.53

-1.96 SD

-0.67

+1.96 SD

1.74

30 32 34 36 38 40

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5


iffe

ren

ce t

1-t

2 (

cm)

Mean

0.39

-1.96 SD

-1.25

+1.96 SD

2.03

30 32 34 36 38 40

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.55

-1.96 SD

-0.86

+1.96 SD

1.96

30 32 34 36 38 40

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.52

-1.96 SD

-0.78

+1.96 SD

1.82


A.2.2 Reproducibility of goniometric measurements (O1-O5)

A.2.2.1 Inter-observer reliability (O1-O5)

Figure 55 shows the inter-observer intraclass correlation coefficients and 95% confidence

intervals for the observers O1, O2, O3, O4 and O5 on the first and second measuring day.

On the first measuring day, the ICC ranged from 0.68 to 0.88, while it ranged from 0.60 to

0.82 on the second measuring day. Considering the measuring position, the ICC for test

position P1 was lower than for position P2.

Position Reliability: ICC [95% CI]

t1 t2

P1 0.68 [0.35 , 0.90] 0.60 [0.27 , 0.86]

P2 0.88 [0.59 , 0.97] 0.82 [0.51 , 0.95]

Table 40: Flexion - Inter-observer reliability (ICC) for observers O1-O5 (n=5)

ICC, intraclass correlation coefficient; CI, confidence interval; P1, first knee joint position; P2, second knee joint

position;


A.2.2.2 Intra-observer reproducibility (O1-O5)

Table 41 and Table 42summarize the results of the intra-observer agreement and reliability

for the observers O1, O2, O3, O4 and O5 and five subjects, respectively. The

corresponding Bland and Altman plots are shown in Figure 55.

Position Observer t1 (°) t2 (°) t1-t2 (°) Lower limit (°) Upper limit (°)


P1 O1 128.0 ± 4.7 130.7 ±5.3 -2.7 [-4.2 to -1.2] 2.1 -6.9 [-9.6 to -4.2] 1.4 [-1.3 to 4.1]

O2 125.2 ±3.8 129.1 ±1.9 -3.8 [-5.5 to -2.2] 2.3 -8.3 [-11.1 to -5.4] 0.6 [-2.3 to 3.4]

O3 125.4 ±5.0 126.1 ±5.3 -0.7 [-2.2 to 0.8] 2.2 -4.9 [-7.6 to -2.2] 3.5 [0.8 to 6.2]

O4 124.6 ±5.8 126.2 ±3.7 -1.6 [-3.9 to 0.7] 3.2 -7.8 [-11.9 to -3.8] 4.7 [0.6 to 8.7]

O5 121.3 ±5.1 124.6 ±4.9 -3.2 [-5.4 to -1.1] 3.0 -9.1 [-12.9 to -5.3] 2.7 [-1.1 to 6.5]

P2 O1 85.5 ±11.0 89.4 ±12.5 -3.9 [-5.5 to -2.4] 2.2 -8.2 [-11.0 to -5.4] 0.4 [-2.4 to 3.2]

O2 87.3 ±8.3 88.1 ±7.5 -0.9 [-3.2 to 1.4] 3.2 -7.2 [-11.2 to -3.1] 5.4 [1.3 to 9.4]

O3 81.0 ±11.6 81.9 ±12.2 -0.9 [-3.9 to 2.1] 4.2 -9.2 [-14.5 to -3.9] 7.3 [2.0 to 12.7]

O4 79.0 ±12.3 80.4 ±11.0 -1.5 [-3.4 to 0.5] 2.7 -6.7 [-10.1 to -3.3] 3.8 [0.4 to 7.2]

O5 81.6 ±10.2 82.8 ±9.9 -1.1 [-2.6 to 0.3] 2.1 -5.2 [-7.8 to -2.6] 2.9 [0.3 to 5.5]

Table 41: Flexion - Intra-observer agreement for observers O1–O5

with mean girth ±SD measured on first and second measuring day, (n=5);

Observer Reliability: ICC [95% CI]

P1 P2

O1 0.80 [0.00 to 0.96] 0.93 [0.06 to 0.99]

O2 0.40 [-0.11 to 0.81] 0.92 [0.73 to 0.98]

O3 0.91 [0.70 to 0.98] 0.94 [0.79 to 0.98]

O4 0.76 [0.31 to 0.93] 0.97 [0.87 to 0.99]

O5 0.69 [-0.01 to 0.92] 0.97 [0.90 to 0.99]

Table 42: Flexion - Intra-observer reliability (ICC) for observers O1-O5 (n=5)

ICC, intraclass correlation coefficient; CI, confidence interval; P1, first knee joint position; P2, second knee joint

position;


Figure 55: Flexion - Intra-observer B-A plots for the observers O1-O5

115 120 125 130 135 140 145

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-2.7

-1.96 SD

-6.9

+1.96 SD

1.4l

r

60 70 80 90 100 110

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-3.9

-1.96 SD

-8.2

+1.96 SD

0.4 l

r

115 120 125 130 135 140 145

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-3.8

-1.96 SD

-8.3

+1.96 SD

0.6l

r

60 70 80 90 100 110

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-0.9

-1.96 SD

-7.2

+1.96 SD

5.4

l

r

115 120 125 130 135 140 145

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-0.7

-1.96 SD

-4.9

+1.96 SD

3.5

l

r

60 70 80 90 100 110

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-0.9

-1.96 SD

-9.2

+1.96 SD

7.3

l

r

115 120 125 130 135 140 145

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-1.6

-1.96 SD

-7.8

+1.96 SD

4.7

l

r

60 70 80 90 100 110

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-1.4

-1.96 SD

-6.7

+1.96 SD

3.8

l

r

115 120 125 130 135 140 145

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-3.2

-1.96 SD

-9.1

+1.96 SD

2.7

l

r

60 70 80 90 100 110

-15

-10

-5

0

5

10


Dif

fere

nce

t1

-t2

(°)

Mean

-1.1

-1.96 SD

-5.2

+1.96 SD

2.9

l

r

Appendix - Additional tables and figures of observers O1 and O2 112

A.3 Additional tables and figures of observers O1 and O2

A.3.1 Reproducibility of girth measurements (first measuring day)

A.1.1.1 Inter-observer reproducibility

Table 43 shows in detail the results of the Bland and Altman analysis with confidence

intervals for the mean difference mD and the lower and upper limits of agreement.

Site Tape O1 (cm) O2 (cm) Agreement: O1-O2 (cm)

Mean ±SD Mean ±SD mD [95% CI] SDdiff Lower limit [95% CI] Upper limit [95% CI]

PP GI 39.1 ± 2.4 38.9 ± 2.5 0.2 [-0.0 to 0.3] 0.5 -0.9 [-1.2 to -0.6] 1.2 [0.9 to 1.5]

GII 40.9 ± 2.5 40.5 ± 2.5 0.4 [0.2 to 0.7] 0.8 -1.1 [-1.7 to -0.8] 2.1 [1.6 to 2.5]

S 40.7 ± 2.5 40.4 ± 2.55 0.3 [0.1 to 0.6] 0.7 -1.0 [-1.4 to -0.6] 1.7 [1.3 to 2.1]

W 39.1 ± 2.4 39.1 ± 2.4 0.0 [-0.1 to 0.2] 0.4 -0.8 [-1.1 to -0.6] 0.9 [0.6 to 1.1]

MP GI 36.7 ± 2.1 36.7 ± 2.0 0.05 [-0.1to 0.2] 0.5 -0.9 [-1.2 to -0.7] 1.0 [0.7 to 1.3]

GII 37.8 ± 2.2 37.8 ± 2.1 -0.1 [-0.3 to 0.1] 0.6 -1.2 [-1.5 to -0.9] 1.0 [0.7 to 1.3]

S 37.8 ± 2.2 37.7 ± 2.1 0.2 [0.05 to 0.3] 0.5 -0.7 [-0.9 to -0.4] 1.1 [0.8 to 1.3]

W 37.1 ± 2.1 37.1 ± 2.0 0.0 [-0.1 to 0.2] 0.4 -0.8 [-1.0 to -0.6] 0.9 [0.6 to 1.1]

DP GI 33.4 ± 2.1 33.6 ± 2.1 -0.2 [-0.3 to -0.1] 0.4 -0.9 [-1.1 to -0.7] 0.5 [0.3 to 0.7]

GII 34.3 ± 2.1 34.5 ± 2.0 -0.2 [-0.4 to -0.1] 0.4 -1.0 [-1.2 to -0.8] 0.6 [0.3 to 0.8]

S 34.5 ± 2.1 34.5 ± 2.0 0.0 [-0.1 to 0.1] 0.4 -0.7 [-1.0 to -0.5] 0.7 [0.5 to 1.0]

W 34.1 ± 2.0 34.3 ± 2.0 -0.2 [-0.3 to 0.0] 0.4 -1.0 [-1.2 to -0.8] 0.6 [0.4 to 0.9]

Table 43: Girth - Inter-observer agreement for first measuring day (O1 and O2)

A.1.1.2 Intra-observer reproducibility

The detailed results of inter-observer agreement analysis for the observers O1 and O2 are

presented in Table 44 and Table 45, respectively. The corresponding Bland and Altman

plots for the measurement sites at mid-patella and 7 cm distal of mid-patella, which were

not shown in the results chapter, are displayed in Figure 56 and Figure 57, respectively.


Site Tape t1 t2

Agreement O1: t1-t2 (cm)

Mean ± SD Mean ± SD mD [95% CI] SDdiff Lower Limit [95% CI] Upper limit [95% CI]

PP GI 39.1 ± 2.4 38.8 ± 2.3 0.1 [-0.2 to 0.3] 0.6 -1.1 [-1.5 to -0.7] 1.3 [0.9 to 1.7]

GII 40.9 ± 2.5 40.7 ± 2.4 0.1[-0.2 to 0.4] 0.8 -1.4 [-1.9 to -1.0] 1.7 [1.2 to 2.2]

S 40.7 ± 2.5 40.3 ± 2.5 0.2 [0.0 to 0.3] 0.5 -0.9 [-1.2 to -0.6] 1.2 [0.9 to 1.5]

W 39.1 ± 2.4 38.8 ± 2.4 0.1 [-0.1 to 0.3] 0.5 -0.9 [-1.2 to -0.6] 1.1 [0.8 to 1.4]

MP GI 36.7 ± 2.1 36.6 ± 2.2 0.1 [0.0 to 0.3] 0.4 -0.7 [-0.9 to -0.4] 0.9 [0.7 to 1.2]

GII 37.8 ± 2.2 37.6 ± 2.0 0.0 [-0.1 to 0.2] 0.5 -0.9 [-1.2 to -0.6] 1.0 [0.7 to 1.2]

S 37.8 ± 2.1 37.7 ± 2.0 0.0 [-0.2 to 0.2] 0.5 -1.1 [-1.4 to -0.8] 1.0 [0.7 to 1.3]

W 37.1 ± 2.1 37.0 ± 2.0 0.0 [-0.2 to 0.2] 0.5 -1.0 [-1.3 to -0.7] 1.0 [0.7 to 1.3]

DP GI 33.4 ± 2.1 33.4 ± 2.3 0.1 [0.0 to 0.3] 0.5 -0.8 [-1.2 to -0.5] 1.1[0.8 to 1.4]

GII 34.3 ± 2.1 34.2 ± 2.2 0.1 [-0.1 to 0.3] 0.5 -0.9 [-1.2 to -0.6] 1.2 [0.9 to 1.5]

S 34.5 ± 2.1 34.5 ± 2.1 0.0 [-0.1 to 0.2] 0.5 -0.9 [-1.2 to -0.6] 1.0 [0.7 to 1.3]

W 34.1 ± 2.0 34.0 ± 2.1 0.1 [-0.1 to 0.3] 0.5 -0.8 [-1.1 to -0.6] 1.1 [0.8 to 1.4]

Table 44: Girth - Intra-observer agreement for observer O1

Site Tape t1 t2

Agreement O2: t1-t2


(cm) (cm) (cm) (cm) (cm)

PP GI 38.9 ± 2.5 38.6 ± 2.5 0.1 [-0.2 to 0.3] 0.6 -1.2 [-1.6 to -0.8] 1.3 [0.9 to 1.7]

GII 40.5 ± 2.5 40.5 ± 2.5 -0.1 [-0.4 to 0.2] 0.8 -1.6 [-2.0 to -1.2] 1.4 [0.9 to 1.8]

S 40.4 ± 2.6 40.2 ± 2.6 0.0 [-0.2 to 0.2] 0.6 -1.1 [-1.5 to -0.8] 1.1 [0.8 to 1.5]

W 39.1 ± 2.4 38.8 ± 2.6 0.1 [0.0 to 0.3] 0.6 -0.9 [-1.3 to -0.6] 1.2 [0.9 to 1.6]

MP GI 36.7 ± 2.0 36.6 ± 2.2 0.0 [-0.1 to 0.2] 0.4 -0.8 [-1.1 to -0.5] 0.9 [0.6 to 1.2]

GII 37.8 ± 2.1 37.7 ± 2.1 0.0 [-0.2 to 0.2] 0.5 -1.1 [-1.4 to -0.8] 1.0 [0.7 to 1.3]

S 37.7 ± 2.1 37.5 ± 2.1 0.0 [-0.1 to 0.2] 0.4 -0.9 [-1.1 to -0.6] 0.9 [0.6 to 1.2]

W 37.1 ± 2.0 36.9 ± 2.1 0.1 [-0.1 to 0.2] 0.4 -0.8 [-1.0 to -0.5] 0.9 [0.7 to 1.2]

DP GI 33.6 ± 2.1 33.5 ± 2.4 0.2 [0.1 to 0.4] 0.4 -0.6 [-0.8 to -0.3] 1.0 [0.8 to 1.3]

GII 34.5 ± 2.0 34.3 ± 2.3 0.2 [0.1 to 0.4] 0.5 -0.8 [-1.1 to -0.5] 1.3 [1.0 to 1.6]

S 34.5 ± 2.0 34.4 ± 2.2 0.2 [0.0 to 0.3] 0.4 -0.7 [-1.0 to -0.5] 1.0 [0.8 to 1.3]

W 34.3 ± 2.0 34.2 ± 2.1 0.1 [0.0 to 0.3] 0.5 -0.8 [-1.1 to -0.5] 1.1 [0.8 to 1.4]

Table 45: Girth - Intra-observer agreement for observer O2


32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.0

-1.96 SD

-0.9

+1.96 SD

1.0 l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

-0.0

-1.96 SD

-1.1

+1.96 SD

1.0l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

-0.0

-1.96 SD

-1.1

+1.96 SD

1.0l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.0

-1.96 SD

-0.9

+1.96 SD

0.9 l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.0

-1.96 SD

-1.0

+1.96 SD

1.0l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

0.9 l

r

Figure 56: Girth - Intra-observer B-A plots at MP for the observers O1 and O2

32 34 36 38 40 42 44

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.7

+1.96 SD

0.9 l

r

32 34 36 38 40 42 44

-2

-1

0

1

2

3

Mean girth GI at MP (O2) (cm)D

iffe

ren

ce t

1-t

2 (

cm)

Mean

0.0

-1.96 SD

-0.8

+1.96 SD

0.9 l

r


Figure 57: Girth - Intra-observer B-A plots at DP for the observers O1 and O2

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.1l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3

Mean girth GI at DP (O2) (cm)D

iffe

ren

ce t

1-t

2 (

cm)

Mean

0.2

-1.96 SD

-0.6

+1.96 SD

1.0l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.9

+1.96 SD

1.2

l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.8

+1.96 SD

1.3

l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.0

-1.96 SD

-0.9

+1.96 SD

1.0 l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.2

-1.96 SD

-0.7

+1.96 SD

1.0l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.1l

r

29 31 33 35 37 39 41

-2

-1

0

1

2

3


Dif

fere

nce

t1

-t2

(cm

)

Mean

0.1

-1.96 SD

-0.8

+1.96 SD

1.1l

r


A.3.2 Reproducibility of knee flexion measurements

A.3.2.1 Inter-observer reliability (first measuring day)

Position O1 (°) O2 (°) O1-O2 (°)

Lower limit (°) Upper limit (°)


P1 112.0 ± 18.1 111.1 ± 17.1 1.0 [0.1 to 1.8] 2.5 -4.0 [-5.4 to -2.5 5.9 [4.5 to 7.3

P2 82.4 ± 8.3 85.1 ± 8.8 -1.1 [-2.3 to 0.1] 3.6 -8.2 [-10.3 to -6.2] 6.0 [3.9 to 8.0]

Table 46: Flexion - Inter-observer reproducibility for O1 and O2 (t1, n=38 legs)

A.1.1.1 Intra-observer reproducibility

Position t1 (°) t2 (°) Agreement: t1-t2 (°)


P1 112.0 ± 18.1 113.8 ± 18.0 -1.8 [-2.8 to -0.8] 2.7 -7.1 [-8.8 to -5.5] 3.6 [1.9 to 5.2]

P2 82.4 ± 8.3 85.1 ± 8.8 -3.2 [-4.0 to -2.4] 2.3 -7.7 [-9.1 to -6.3] 1.2 [-0.1 to 2.6]

Table 47: Flexion - Intra-observer reproducibility for observer O1 (n=34 legs)

Position t1 (°) t2 (°) Agreement: t1-t2 (°)


P1 111.1 ± 17.1 112.8 ± 17.3 -1.9 [-3.0 to -0.8] 3.2 -8.1 [-10.0 to -6.2] 4.3 [2.4 to 6.2]

P2 83.6 ± 6.58 84.0 ± 6.3 -0.8 [-1.9 to 0.4] 3.3 -7.1 [-9.1 to -5.2] 5.6 [3.6 to 7.6]

Table 48: Flexion - Intra-observer reproducibility for observer O2 (n=34 legs)

Appendix - Additional figures of clinical course measurements 117

A.4 Additional figures of clinical course measurements

Figure 58: Relationship between mean girth at MP and mean passive ROM

Figure 59: Relationship between mean girth at DP and mean passive ROM

0

20

40

60

80

100

120

140

35

37

39

41

43

45

47

-1 1 2 3 4 5 6 7

Pa

ssiv

e R

OM

(°)

Gir

th (

cm)

Days after TKA

Mean girth at MP Mean passive ROM

0

20

40

60

80

100

120

140

35

36

37

38

39

40

41

-1 1 2 3 4 5 6 7

Pa

ssiv

e R

OM

(°)

Gir

th (

cm)

Days after TKA

Mean girth at DP Mean passive ROM

Appendix - Additional figures of clinical course measurements 118

Figure 60: Relationship between mean Girth at MP and maximum reported NRS

Figure 61: Relationship between mean Girth at DP and maximum reported NRS

1

2

3

4

5

6

7

8

9

10

40

41

42

43

44

45

-1 1 2 3 4 5 6 7

Ma

xim

um

NR

S

Gir

th [

cm]

Days after TKA

Mean girth at MP Mean NRSmax

1

2

3

4

5

6

7

8

9

10

34

36

38

40

42

-1 1 2 3 4 5 6 7

Ma

xim

um

NR

S

Gir

th [

cm]

Days after TKA

Mean girth at DP Mean NRSmax

Appendix - Questionnaire on the usability of the measuring tapes 119

Questionnaire on the usability of the measuring tapes

used in this study (Gulick I, Gulick II plus, standard, and Waegener tape

measures) (translated from German)

Please take some time to answer the following questions on the measuring tapes used!

Observer number:

1. What is your gender?

☐ male ☐ female

2. Did you have any experience in circumferential leg measurements prior to this

study?

☐ yes ☐ no

3. Please list the measuring tapes used in this study according to their usability!

Note: 1. Most user-friendly

4. Least user-friendly

1.

2.

3.

4.

Please mark with a cross where applicable!

Gulick I Gulick II plus Standard Waegener


4. What did you like most about the tape measure you ranked first?

Does apply Does not apply

Easy handling ☐ ☐

Precise measurement ☐ ☐

Measurements taken quickly ☐ ☐

Thick tape ☐ ☐

Thin tape ☐ ☐

Numbers easy to read ☐ ☐

Zero line clearly visible ☐ ☐

Tape easy to position ☐ ☐

Tape doesn´t slip ☐ ☐

Space for comments:

5. What did you dislike about the measuring tape you ranked lowest?

Does apply Does not apply

Complicated handling ☐ ☐

Inaccurate measurement ☐ ☐

Measuring takes long ☐ ☐

Thick tape ☐ ☐

Thin tape ☐ ☐

Numbers difficult to read ☐ ☐

Zero line difficult to identify ☐ ☐

Difficult positioning of tape ☐ ☐

Tape slips easily ☐ ☐

Space for comments:


6. Which is the most accurate tape measure in your opinion?

☐ Gulick I ☐ Gulick II plus ☐ Standard ☐ Waegener

7. Which do you think is the least accurate tape measure?


8. With which tape measure can the measurements be taken fastest?


9. Which tape measure takes the longest?


10. Do you feel that your measuring accuracy decreased with the duration of the

measurement procedure (because you got tired)?

☐ Yes ☐ No

11. Do you think that your measuring accuracy increased with the duration of the

measurement procedure (because you got used to handling the measuring tapes)?

☐ Yes ☐ No


12. Space for personal remarks

Pros Cons

Standard tape measure

Waegener tape measure

Gulick I tape measure

Gulick II plus tape measure

Thank you for your time!

Appendix- Probandeninformation/Einwilligungserklärung Seite 123

Probandeninformation/Einwilligungserklärung

zur Teilnahme an der Studie

Umfangs- und Winkelmessungen im Kniebereich

Sehr geehrte Teilnehmerin, sehr geehrter Teilnehmer!

Ich lade Sie ein an der oben genannten Studie im Rahmen meiner Diplomarbeit teilzunehmen.

Ihre Teilnahme an dieser Studie erfolgt freiwillig. Sie können jederzeit ohne Angabe von

Gründen aus der Studie ausscheiden.

Studien sind notwendig, um verlässliche neue medizinische Forschungsergebnisse zu

gewinnen. Unverzichtbare Voraussetzung für die Durchführung einer Studie ist jedoch,

dass Sie Ihr Einverständnis zur Teilnahme an dieser Studie schriftlich erklären.

Bitte unterschreiben Sie die Einwilligungserklärung nur

- wenn Sie Art und Ablauf der Studie vollständig verstanden haben,

- wenn Sie bereit sind, der Teilnahme zuzustimmen und

- wenn Sie sich über Ihre Rechte als Teilnehmer an dieser Studie im Klaren sind.

1. Was ist der Zweck der Studie?

Der Zweck dieser Studie ist es, eine Messmethode zur Bestimmung des Beinumfanges im

Kniebereich zu evaluieren, sowie die Messmethode zur Bestimmung der

Kniegelenksbeugung mittels Goniometer auf ihre Genauigkeit zu überprüfen.

2. Wie läuft die Studie ab?

Der Beinumfang jedes Beins wird an drei verschiedenen Messpunkten im Bereich des

Kniegelenks mit vier verschiedenen Maßbändern gemessen. Für die Umfangsmessung

wird das jeweilige Bein auf einer Papierrolle gelagert. Als Referenz für die Messpunkte

wird die Kniescheibe herangezogen. Die Position der Kniescheibe wird zunächst durch

Ertasten ermittelt und die obere und untere Begrenzung auf einem zuvor geklebten Pflaster

markiert. Dann wird die Mitte der Kniescheibe ermittelt. Dies ist der erste Messpunkt. Die

beiden weiteren Messpunkte liegen 7 cm über bzw. 7 cm unter dem ersten Messpunkt. Da

die drei Messpunkte von jedem Prüfer neu auf einem Pflaster markiert werden und daher

das Pflaster nach den Messungen jedes Prüfers entfernt wird, wird den Teilnehmern vor

Beginn der Messungen ein Strumpf angezogen, sodass das Pflaster nicht direkt auf die


Haut geklebt werden muss. Um die Genauigkeit der Methode zu überprüfen, wird an jeder

Messstelle drei Mal gemessen. Die Beugung im Kniegelenk wird mit einem Goniometer in

drei verschiedenen Beugepositionen bestimmt. Dazu wird das jeweilige Bein in einer

speziellen Vorrichtung gelagert. Auch hier wird die Messung drei Mal wiederholt, um die

Genauigkeit der Methode zu überprüfen.

3. Gibt es Risiken, Beschwerden und Begleiterscheinungen?

Die Messungen sind für die/den (kniegesunden) TeilnehmerIn schmerzfrei.

4. Hat die Teilnahme an der Studie sonstige Auswirkungen auf die Lebensführung

und welche Verpflichtungen ergeben sich daraus?

Keine

5. In welcher Weise werden die im Rahmen dieser Studie gesammelten Daten

verwendet?

Nur die Prüfer und deren Mitarbeiter haben Zugang zu den vertraulichen Daten, in denen

Sie namentlich genannt werden. Diese Personen unterliegen der Schweigepflicht.

Die Auswertung und- wenn dafür nötig- die Weitergabe der erhobenen Daten erfolgt

ausschließlich zu in anonymisierter Form. Auch zur etwaigen Veröffentlichung der

Ergebnisse dieser Studie werden nur anonymisierte Daten verwendet und Sie nicht

namentlich erwähnt.

6. Möglichkeit zur Diskussion weiterer Fragen

Für weitere Fragen im Zusammenhang mit dieser Studie stehen Ihnen Ihre Prüfer gern zur

Verfügung. Auch Fragen, die Ihre Rechte als Teilnehmer an dieser Studie betreffen,

werden Ihnen gerne beantwortet.

Namen der Kontaktpersonen:

Daniela Hirzberger Ass. Prof. Dr. Mathias Glehr

Universitätsklinik für Orthopädie, Graz Universitätsklinik für Orthopädie, Graz

Erreichbar unter: 0676 67 20 464 Erreichbar unter: 0316 385-81756


7. Einwilligungserklärung

Name des Teilnehmers in Druckbuchstaben:

...........................................................................

Geb.Datum: ....................................... Code: ..........................................................

Ich erkläre mich bereit, an der Studie „Umfangs- und Bewegungsmessungen“

teilzunehmen.

Ich bin von Herrn Ass.-Prof. Dr. Mathias Glehr ausführlich und verständlich über

mögliche Belastungen und Risiken, sowie über Wesen, Bedeutung und Tragweite der

Studie und sich für mich daraus ergebenden Anforderungen aufgeklärt worden. Ich habe

darüber hinaus den Text dieser Patientenaufklärung und Einwilligungserklärung, die

insgesamt 3 Seiten umfasst, gelesen. Aufgetretene Fragen wurden mir vom Prüfer

verständlich und genügend beantwortet. Ich hatte ausreichend Zeit, mich zu entscheiden.

Ich habe zurzeit keine weiteren Fragen mehr.

Ich werde den Anordnungen, die für die Durchführung der Studie erforderlich sind, Folge

leisten, behalte mir jedoch das Recht vor, meine freiwillige Mitwirkung jederzeit zu

beenden.

Ich bin zugleich damit einverstanden, dass meine im Rahmen dieser Studie ermittelten

Daten aufgezeichnet werden. Um die Richtigkeit der Datenaufzeichnung zu überprüfen,

dürfen Beauftragte des Auftraggebers und der zuständigen Behörden (z.B. Medizinische

Universität Graz) beim Prüfer Einblick in meine personenbezogenen Daten nehmen.

Beim Umgang mit den Daten werden die Bestimmungen des Datenschutzgesetzes

beachtet. Eine Kopie dieser Patienteninformation und Einwilligungserklärung können Sie

auf Wunsch erhalten. Das Original verbleibt beim Prüfer.

......................................................................................................

(Datum und Unterschrift der Teilnehmerin/des Teilnehmers)

......................................................................................................

(Datum, Name und Unterschrift des verantwortlichen Prüfers)

Reproducibility of circumferential leg and knee joint ...

Documents